Patent Application
20240034447
The present disclosure relates generally to deep-sea mining systems and more specifically to a dynamic buoyancy system for a deep-sea mining system. The dynamic buoyancy system applies variable buoyancy conditions that allow the deep-sea mining system to descend, collect ore nodules from the seabed, and ascend without seabed contact to limit the environmental impact.
As the world transitions to green energy solutions, there is a growing demand to store energy in reusable batteries made from critical metals such as nickel, copper, and cobalt. Currently, there are fewer sources of these metals remaining on land and these land-based resources can be in challenging places and/or within sensitive ecosystems. Deep sea mining is an un-tapped source of critical metals in the form of ore nodules (e.g., polymetallic ferromanganese nodules) and has been the focus of the mining industry in recent years.
Technical difficulties associated with deep-sea mining include the ocean depths (e.g., 5 km to 6 km) and the extreme pressures (e.g., between 500 bar and 600 bar) at which the mining of the ore nodules occurs, and the techniques required to transport the mined ore up to the ocean surface. There are two systems that have been widely examined and determined feasible on a small scale: (i) seabed dredging collector systems that pump the ore to the surface as a slurry through vertical riser pipes, and (ii) mechanical lifting systems that use synthetic ropes. However, both systems suffer from reliability and scaling issues, and can cause irreparable damage to sensitive environments due to the disturbances caused on the seabed during the mining process.
Therefore, there is a need for more sustainable ways to harvest minerals from the sea floor whilst keeping the seabed ecosystem intact.
A dynamic buoyancy system implemented for deep-sea mining systems and methods for using the same are disclosed herein. According to some embodiments, the disclosed dynamic buoyancy system enables the deep-sea mining system to hover at a predetermined distance from the seabed during the entire mining process, which minimizes the environmental impact of the mining process. Further, the deep-sea mining system using the dynamic buoyancy system disclosed herein can be scaled and deployed as a fleet of vehicles with redundancy. According to some embodiments, the dynamic buoyancy system enables the deep-sea mining system to descend to the seabed, travel along the seabed without contact while collecting the ore nodules, and ascend to the surface to deliver its payload. The dynamic buoyancy system applies variable buoyancy techniques and employs opposer/thrust devices designed to work in a power-reduced mode at the planned ocean depths as the deep-sea mining system descends, collects ore, and ascends without seabed contact and with minimum environmental impact.
The accompanying figures, which are included as part of the present specification, illustrate the presently preferred embodiments and together with the general description given above and the detailed description of the preferred embodiments given below serve to explain and teach the principles described herein.
In deep-sea mining, as weight is added or removed from an underwater vehicle, buoyancy acting on the vehicle changes. It is therefore necessary to compensate for the buoyancy changes attributed to weight loss or weight gain. The use of air bladders that expand and displace water is an approach for adjusting buoyancy underwater. Because water becomes more dense with increasing pressure (e.g., at the depths where polymetallic nodules can be found and collected), more air is required to achieve the same amount of lift.
According to some embodiments, UAV 130 is equipped with thrusters (not shown in
According to some embodiments, deep-sea mining system 100 uses underwater surveying and inspection systems to locate the ore nodules 120 on the seabed and to determine whether marine life is anchored on the nodules. By way of example and not limitation, deep-sea mining system 100 may be configured to avoid collecting ore nodules having marine life anchored on them. Once the payload hoper 150 is full, the dynamic buoyancy system 160 enables the deep-sea mining system 100 to ascend to the sea surface and deliver its payload. In some embodiments, the dynamic buoyancy system 160 is configured to keep the deep-sea mining system 100 neutrally buoyant at any depth, and in particular close to the operating depth, while limiting the use of electrically powered thrusters to conserve energy.
According to some embodiments, the components of deep-sea mining system 100 (e.g., dynamic buoyancy system 160, payload hopper 150, ore collector system 140, and UAV 130) operate in synergy. In some embodiments, these components may be either integrated in a single housing or operated as detachable modules physically and communicatively connected to one another. According to some embodiments, dynamic buoyancy system 160, payload hopper 150, ore collector system 140, and UAV 130 are physically attached to one another during the collection/mining process, and at least the payload hopper 150 and the dynamic buoyancy system 160 can be physically attached to one another during the mining and ascending process. In some embodiments, the dynamic buoyancy system 160 can provide the necessary buoyancy to compensate for the collected ores during the mining process and the ascent of at least the payload hopper 150 or of the entire deep-sea mining system 100. In some embodiments, if the dynamic buoyancy system 160 and the payload hopper 150 ascend on their own to the ocean surface, UAV 130 may provide with its thrusters the necessary buoyancy to deep-sea mining system 100 until the dynamic buoyancy system 160 and the payload hopper 150 descend again from the sea surface to re-attach to the deep-sea mining system 100.
In some embodiments, deep-sea mining system 100 can include additional components, modules, and systems necessary for its indented operation. These additional components, modules, and systems are not shown in
Autonomous or untethered submersible vehicles, such as the deep-sea mining system 100, operate on a finite amounts of power. More often than not, submersible vehicles use electric energy for producing propulsion/thrust. When the lift or buoyancy adjustments for a submersible vehicle are thrust based, there can be a substantial increase in power and propulsion demand, which translates to a continuous power usage of the vehicle's energy resources.
On the other hand, increasing the power storage of a submersible vehicle, increases the vehicle's mass and volume, which is not desirable. In aircraft design, lift, thrust for lift/speed, and weight are parameters carefully considered. For example, for a new aircraft design, when the mass of the aircraft increases, the lift acting on the wings of the new aircraft has to increase to offset the added mass. Lift increases by increasing: (i) the wing surface area, which adds more weight; and (ii) the provided thrust, which requires larger and heavier engines. A larger wing span also means a higher fuel capacity, which also adds weight. Therefore, there is a sequence of reciprocal cause and effect in which two or more elements intensify and aggravate each other. The system described herein interrupts this reciprocal cause and effect cycle.
As the mass to be lifted increases and the time of non-static operation increases, the weight of the vehicle and the power requirements increase. For example, the energy transferred to an object (e.g., the work done W) via the application of force F along a displacement S is provided by equation (1) below:
W(Joules)=F(Newtons)·S(meters) (1).
The work W performed during a period with duration t is provided by equations (2) below.
W(Joules)=P(Watts)·t(seconds) (2),
where P is the power or amount of energy transferred per unit time.
Time domain complications exist when buoyancy sources interact with large changes in mass. As a result, related rates can cause the control algorithms governing these interactions to be non-trivial. In addition, submersible vehicles are mostly concerned with observation or interaction tasks. Therefore, autonomous submersible vehicles tasked with very large-scale collection of mass are rare. Autonomy and relative collection of mass as a ratio to raw vehicle mass is even rarer. Accordingly, there are no known or established methods of energy reduction in prior systems. Advantageously, the deep-sea mining system 100 disclosed herein is equipped with an opposer/thrust device that minimizes its energy consumption during operation.
According to some embodiments, thrusters of a submersible vehicle generate energy-consuming dynamic buoyancy (DB) with respect to their scalar volume. On the other hand, non-energy consuming sources, such as lift bags, produce static buoyancy (SB). Accordingly, a submersible vehicle equipped with both lift bags (also referred herein as “opposers”) and thrusters, referred to herein collectively as opposer/thruster devices, would have, at any given time, a total resultant buoyancy (RB) as provided by equation 3 below:
RB=SB+DB (3).
According to some embodiments, the amount of dynamic buoyancy DB generated is proportional to the amount of energy E consumed (e.g., DB∝|E|). And because both negative and positive DB consume energy E or power P, the latter being defined as the amount of energy consumed per unit time (e.g., P=dE/dt), it would be desirable to minimize the need for dynamic buoyancy DB to drive the power P (e.g., the energy consumed per unit time) to a minimum (e.g., DB→0, P→0). However, to maintain the total resultant buoyancy RB constant (or within acceptable levels) according to equation 3, the static buoyancy SB has to compensate for the loss in dynamic buoyancy DB. In other words, minimizing DB requires maximizing SB to maintain a constant RB.
Challenges with Opposer/Thrust Devices
When a lift bag filled with a gas or gas mixture (e.g., air) is submerged into water, changes in the water pressure result in an inverse change of the gas volume within the lift bag as described by Boyle's law, which states that the pressure of a system is inversely proportional to its volume (e.g., P∝V−1). For example, when a balloon filled with air descends into a water column, the water pressure (e.g., the hydrostatic pressure) surrounding the balloon increases as a function of depth. The increasing water pressure compresses the balloon whose volume begins to decrease (V↓) as the hydrostatic pressure increases. At the same time, the balloon's internal pressure increases (P↑) according to Boyle's law. Conversely, when the balloon ascends, the hydrostatic pressure decreases, which allows the gas inside the balloon to expand. This also causes the balloon's volume to increase (V↑) according to Boyle's law.
Because the buoyancy acting on the balloon is proportional to its volume (which defines the amount of water being displaced), the buoyancy increases as the balloon expands during its ascent and decreases as the balloon shrinks during its descent. Accordingly, during the balloon's ascent or descent, the buoyancy acting on the balloon changes at a variable rate as a function of depth until the fluid resistance increases to the point where an equilibrium condition is reached. This means that a lift bag filled with a fixed amount of gas may experience changes in its buoyancy when its vertical position changes (e.g., its depth in a column of water). And because, as explained above, the buoyancy changes at a variable rate, the buoyancy may overshoot in either direction (e.g., become either very positive or very negative) depending on whether the lift bag ascends or descends. This effect is known as SB overshoot. Due to this effect, the SB produced by lift bags in opposer/thrust devices may become variable if left unchecked. Accordingly, lift bags or similar sources of SB may require modifications for deep-sea operation. For example, a system is required to inject and release gas from the lift bag during the descent and ascent to account for the changes in hydrostatic pressure.
In addition, it is necessary to control second order effects or time delay effects, such as the rate at which the SB changes when gas is injected into or released from the lift bag of an opposer/thrust device. SB produced by lift bags stabilizes slowly as the gas settles (e.g., as the gas reaches an equilibrium state within the volume of the lift bag), which can be substantially lower than the rate at which the DB produced by thrusters changes (e.g., dSB/dt<dDB/dt). For instance, when compressed air is introduced into a lift bag submerged in water, it can take up to 30 s for the gas to settle and for the buoyancy vector to stabilize. In contrast, DB provided by a thruster is practically instantaneous. Therefore, when gas is injected in the lift bag of an opposer/thruster device, DB from the thruster may be used to counteract the second order effects—e.g., until the gas settles in the lift bag. This also applies for when gas is released from the lift bag.
The combination of secondary effects with the SB overshoot makes the use of opposer/thrust devices challenging for deep-sea operations. Nevertheless, power savings can be realized when SB is used instead of DB in scenarios where the load or weight of the deep-sea mining vehicle changes during the mining process. For example, when the buoyancy generated by SB devices offsets the weight of the load while DB is judiciously used to prevent overshoot and second order effects.
Because maximizing the use of SB increases the probability of an overshoot incident or secondary effects, a balanced amount of DB may be necessary in an opposer/thrust device as discussed above. This balanced amount of DB may be optimized based on the existing conditions to minimize the consumption of energy. For example, an amount of power may be budgeted for maneuvering the submersible vehicle when the load or weight of the vehicle changes.
According to some embodiments, a lift or a positive buoyancy source is a gas-driven lift bag with or without the ability to release gas except in overpressure conditions. Lift bags are rubber enclosures with straps used in underwater environments. Air is a commonly used gas mixture injected into the bag via a compressed air housing. In some embodiments, the gas pressure inside the lift bag is greater than the surrounding underwater pressure. If the lift bag is equipped with a release valve, by operating the release valve, gas may escape through the valve from the lift bag into the surrounding water due to the pressure differential.
Overpressure, as used herein, describes the condition where the lift bag is allowed to release air via a release valve to maintain its structural integrity. In the event that pressure release is not an option when there is lift (e.g., positive buoyancy), a negative thrust is necessary to counteract the lift. Once the ascent from the lift begins, lift bag volume expansion occurs due to Boyle's law until a maximum amount of lift is achieved (e.g., when drag prevents the lift from increasing further).
Over time, by slowly tuning SB lift and using limited amounts of thrust in the form of DB, energy consumption may be limited to small amounts as compared to situations where thrust alone is used to compensate for load or weight increase, according to some embodiments. For example, a control loop system may be used to provide limited amounts of DB via thrusters while SB produced by lift bags is used to provide the majority of the buoyancy required to offset the load or the weight increase.
According to some embodiments,
In some embodiments, lift bag 210 is a rubber enclosure equipped with at least one gas valve 230 located at its base 210B and one or more pressure release valves 240 located at one or more side surfaces 210S. However, this is not limiting, and release valves 240 may be placed in other suitable locations on the lift bag (e.g., at a top or at a bottom surface.) According to some embodiments, gas valve 230 is a one-way valve. This means that gas valve 230 allows gas to be injected into lift bag 210 but prevents gas from escaping lift bag 210. One or more gas cylinders 250 containing compressed gas (e.g., air or any other suitable gas mixture) provide gas to lift bag 210 via a gas valve 230. In some implementations, lift bag 210 has an elliptical shape with its long axis along the vertical direction z, as shown in
According to some embodiments, thruster 220 provides DB to mitigate overshoot incidents or secondary effects by preventing or counterbalancing the vertical displacement of lift bag 210 while lift bag 210 is operated—e.g., when gas is injected or released from lift bag 210. In some embodiments, thruster 220 may provide thrust along the x and y directions, in addition to the z direction. In some embodiments, thruster 220 may be limited to providing thrust in the vertical direction z while additional thrusters (not shown in
In some embodiments, power reduction in descent can be achieved by controlling the rate of descent with lift. For instance, and during the descent, the gas delivery can be adjusted so that the gas injected into lift bag 210 reduces the rate at which the volume of lift bag 210 shrinks. Gas injection in lift bag 210 via valve 210B increases the gas pressure and counterbalances the volume compression from the increasing hydrostatic pressure. Therefore, by regulating the amount of gas injected in the lift bag, one can control the volume compression of the lift bag 210, and thus, the rate of its descent. In other words, as the opposer/thruster device 200 descents, gas injection in lift bag 210 may increase at a rate that counterbalances the rate at which the volume of lift bag 210 shrinks due to the increasing hydrostatic pressure so that the volume of lift bag 210 shrinks at a controlled rate. This would allow the opposer/thruster device 200 to descent at any desirable rate irrespective of the hydrostatic pressure and avoid overshoot incidents.
In some embodiments, pressure sensors can provide pressure readings for the hydrostatic pressure and the gas inside the lift bag 210. Suitable electronic equipment (e.g., a controller) may then calculate the rate at which the pressure inside the lift bag increases as a function of the hydrostatic pressure changes. Based on this information, the gas injection may be adjusted to control the rate of descent. If a proper gas delivery adjustment is made, overshoot is prevented and thrust may only be used to allow for recovery from secondary effects. According to some embodiments, pressure compensated gas regulation may be used for the gas supply of lift bag 210 in opposer/thrust device 200.
A similar concept applies to the ascent. For example, the ascent rate may be controlled by regulating the gas release via the pressure release valves 240. In some embodiments, the gas supply system may be responsible for operating pressure release valves 240. In some embodiments, the same logic that operates the gas supply system may also operate the pressure release valves 240. In some embodiments, a different system from the gas supply system may operate the pressure release valves 240. As the buoyancy system ascents and the volume of lift bag 210 increases, gas may be released via the release valves 240 at a rate comparable to the volume increase rate to control the ascent rate. In some embodiments, DB produced by thrusters 220 may be used to mitigate the impact of secondary effects.
In an ideal scenario, the opposer/thruster device 200 keeps the submersible vehicle (e.g., the deep-sea mining system 100) in a neutrally buoyant state during the ore collection process. This means that the submersible vehicle is able to hover over the ocean floor with minimal effort and with no need to produce large amounts of DB. To sustain neutral buoyancy, lift bag 210 can be supplied with gas at frequent intervals (or as required) to produce sufficient lift to counteract the variable load 230. For example, as the weight of the variable load 230 increases, an onboard computer may calculate the amount of gas or air required to generate enough lift to offset the weight of variable load 230 based on the hydrostatic pressure of the surrounding water. In some embodiments, thruster 220 may provide some amount of DB to prevent SB overshooting and to eliminate any secondary effects during the gas injection process.
According to some embodiments, onboard systems and detectors may continuously collect data and dynamically calculate the amount of lift required to offset the payload weight based on the current hydrostatic pressure conditions. Based on this information, an appropriate amount of gas or air may be injected into lift bag 210 while thruster 220 may intervene to make minor corrections or when there are issues detected with the gas supply system of opposer/thruster 200.
According to some embodiments, multiple opposer/thruster devices may be used to control a large weight lift from a common control, gas source, and power source. Multiple points can reduce local thrust effects close to a water body's bottom, and as such will provide less silt, reduce ecological disturbances and allow identification of items for collection. By coordinating local pressure values (e.g., using digital logic controlling electric actuators such as solenoid valves), it is possible to use multiple opposer/thrust devices to control a large weight lift, the orientation and angle of the collection vehicle's load, etc.
For example,
A single opposer/thruster device can be used for moving diver assisted or vehicle assisted large loads—e.g. in commercial diving. When the orientation (pitch and roll) of the load being raised doesn't matter, a single opposer/thruster device may be used. Multiple thrusters would allow for emergency recovery, should an opposer fails.
The opposer/thruster device disclosed herein is not limited to deep-sea operations or the deep-sea mining system 100. According to some embodiments, energy efficient opposer/thruster device 200 may be used for any underwater activity related to lifting large loads and/or maintaining neutral buoyancy in underwater vehicles or objects for extended periods of time.
The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
The term “approximately”, the phrase “approximately equal to”, and other similar phrases, as used in the specification and the claims (e.g., “X has a value of approximately Y” or “X is approximately equal to Y”), should be understood to mean that one value (X) is within a predetermined range of another value (Y). The predetermined range may be plus or minus 20%, 10%, 5%, 3%, 1%, 0.1%, or less than 0.1%, unless otherwise indicated.
The indefinite articles “a” and “an,” as used in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
As used in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.
As used in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof, is meant to encompass the items listed thereafter and additional items.
Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed. Ordinal terms are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term), to distinguish the claim elements.
Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
This application claims the benefit of U.S. Provisional Patent Application No. 63/394,199, titled “PROCESSES AND METHODS FOR BINARY OPPOSING BUOYANCY FOR LARGE UNDERWATER LIFT APPLICATIONS,” which was filed on Aug. 1, 2022 and is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63394199 | Aug 2022 | US |
