WO2019164624A1

WO2019164624A1 - Wave-energy converter systems and methods related thereto

Info

Publication number: WO2019164624A1
Application number: PCT/US2019/014809
Authority: WO
Inventors: Philip Lawrence SWAN
Original assignee: Aquaring Energy, Inc.
Priority date: 2018-01-23
Filing date: 2019-01-23
Publication date: 2019-08-29

Abstract

Systems for converting wave energy to electrical energy and other useful forms of work are disclosed herein. Methods of making and using the systems are also disclosed herein. Some of the systems include both a wave-energy converter and an integrated inertial energy storage system. Other systems do not include the integrated inertial energy storage system.

Description

Wave-Energy Converter Systems and Methods Related Thereto

Background of the Invention

This invention pertains to renewable energy generation through wave energy conversion.

Wind acting on the surface of a body of water, and, less frequently, seismic events below the body of water, will create waves. Wind-generated wave energy is concentrated near the surface of a deep body of water. In a sufficiently large body of deep water, such as an ocean, wave energy from localized sources, such as thunderstorms, is well distributed. Consequently, in many locations, wave energy from one or more local or distant sources is, effectively, ever-present.

Other sources of renewable energy are intermittent. Wind is inconsistent. Solar energy is unavailable during the night and may be affected by cloud cover during the day. Tides stop ebbing or flowing four times each day. Some sources of

hydroelectricity may become unavailable during dry spells.

Demand for energy also varies throughout the day. The most valued energy generation systems are those that dependably deliver power when demand peaks. If a renewable energy generation system is not reliable when demand peaks the capital cost of building and later decommissioning a polluting power plant may be justified, because it is essential for the grid to always be able to meet demand. When this is the case, the renewable energy technology’s cradle-to-grave costs have to compete with the relatively low incremental cost of additionally operating the polluting power plant during non-peak hours. However, if a renewable technology is dependable when demand peaks, then it can substitute for the polluting power plant. The renewable technology will then be more competitive because its cost will be evaluated against the polluting power plant’s full cradle-to-grave cost as opposed to its incremental operational cost.

The terms“Levelized Cost of Energy” (LCoE) and“Levelized Avoided Cost of Energy” (LACE) are relevant metrics that the industry uses to help distinguish between the different competitive situations. LCoE is the total cradle-to-grave cost of a plant divided by the watt-hours it produces over its lifetime. LACE compares the cost of each MWh from a new plant with the cost of a MWh that it displaces. LACE is the avoided costs from other sources divided by the annual yearly output of the non- dispatchable source.

As two-thirds of the Earth’s land mass is covered by water, there are ample places to situate wave energy conversion technology. On the other hand, the number of suitable sites for hydroelectric and geothermal energy generation are relatively limited by geography. Nuclear power plants are difficult to site because they are unpopular due to the widespread and costly environmental damage that they cause from time to time. Bio-fuel production makes inefficient use of rural real estate.

Fossil fuel energy generation has few restrictions concerning where it can be situated. For now, it is a very dependable form of energy. Flowever, it drains irreplaceable planetary resources. It creates immediate environmental problems such as oil spills and smog. Efforts to rein in its increasing cost lead to expensive military conflicts and loss of life. Its ongoing use is anticipated to create future environmental problems of unknown proportion. Because of these less tangible factors, the true cost of fossil fuel may, in fact, be unacceptably high.

Past efforts to implement wave energy conversion have revealed challenges.

Bio-fouling, ocean debris entanglement, and corrosion limit the time that exposed mechanical components can be relied upon to operate properly in a marine

environment. Several technologies have partially addressed this by placing some of the system’s components on-shore. Flowever, because the amount of affordable shoreline real estate is limited, this solution compromises the technology’s scalability. The remaining components are still subject to bio-fouling, entanglement, and corrosion. Thus, either the system’s value depreciates to zero before it has

converted enough energy to break even, or the system’s ongoing maintenance costs impede profitability.

Availability (that is, the ability to provide power whenever power is needed) is an important performance metric for renewable energy generation technologies including wave energy generators. Some designs need to be taken off-line and secured during stormy weather, leading to lower availability. Others are liable to be damaged and go off-line during severe storms or if they encounter a rogue wave or tidal wave.

A successful wave energy conversion technology must be scalable. Some proposed technologies are visually obtrusive. Others use up coastal real estate when they are implemented. If such technologies were implemented on a large scale, they would negatively impact the beauty of a coastline or they would mar the scenic views that attract tourists and contribute to the value of coastal real estate. Advocacy groups might object to the implementation of these technologies on a large scale, which would hinder widespread deployment of the technology.

Brief Summary of the Invention

Systems are disclosed herein for converting wave energy to electrical energy and other useful forms of work. The systems may comprise an outer shell configured to be suspended in a body of water and configured to move with waves in the body of water. The systems may further comprise a rigid interior element located at least partially within the outer shell and configured to resist movement with waves in the body of water. The systems may further comprise a power take-off unit operably connected to an inside of the outer shell and operably connected to the rigid interior element. The power take-off unit may convert motion of the outer shell relative to the rigid interior element into electrical energy or apply mechanical work to another system.

In some embodiments, the rigid interior element comprises a ring located entirely within the outer shell. The ring may comprise a rotatable ring configured to continuously rotate within the outer shell during operation and thereby resist lateral movement as the outer shell is moved by waves in the body of water. The system may further include a support structure configured to support the rotatable ring and be operably connected to the power take-off unit. For example, the support structure may comprise a levitation system that utilizes magnetic forces to levitate the rotatable ring. The levitation system may be configured to use electrical energy to increase the rate of rotation of the rotatable ring. Likewise, the levitation system may be configured to convert kinetic energy of the rotatable ring into electrical energy. Alternatively, the ring may comprise a stationary ring and a plurality of power take-off units that are operably connected to the stationary ring in opposition to each other and thereby resist lateral movement as the outer shell is moved by waves in the body of water.

The systems may include an anchor and a cable attached to the outer shell and independent of the rigid interior element.

In some embodiments, the rigid interior element comprises a cable or rod. For example, a cable or rod may be operably connected to two anchor points and placed under tension to thereby resist lateral movement as the outer shell is moved by waves in the body of water. In such embodiments, the outer shell may circumscribe all or a portion of the cable or rod.

In some embodiments, all moving parts used to convert mechanical energy to electrical energy are contained within the outer shell and are isolated from the body of water during operation.

In some embodiments, the outer shell comprises segments that are flexible relative to each other, wherein a first portion of the outer shell is capable of moving in one direction and a second portion of the outer shell is capable of moving in a different direction as the outer shell is moved by waves in the body of water.

The outer shell may have a variety of configurations, such as a circular cross-section. In some embodiments, the power take-off unit comprises a generator for converting linear mechanical energy into electrical energy. There may be a plurality of power take-off units operably connected to a support structure for the rigid interior element, wherein the plurality of power take-off units are juxtaposed relative to each other and are each operably connected to the inside of the outer shell.

In some embodiments, the rigid interior element comprises a ring and the outer shell is toroidally shaped.

The systems may include a dual-purpose cable that contains at least one insulated wire operably connected to the power take-off unit and configured to carry power away from the system and that also serves to anchor the system within the body of water.

The systems may include a depth control system that can vary the depth of the outer shell.

Methods of making the systems are also disclosed herein. For example, a method of making systems where the rigid interior element is a ring may include using a combined assembly and autoclave machine that travels around the interior of the outer shell and sequentially surrounds a portion of the ring, until the ring is formed within the outer shell. The methods may include disassembly and removal of the combined assembly and autoclave machine and then installation of the power take- off unit.

Methods of using the systems are also disclosed herein. For example, a method of generating electricity or other useful forms of work from waves may include

characterizing the wavelength of waves in a body of water and then deploying the systems disclosed herein in the body of water to a depth where the maximum radius of the outer shell is greater than a hypothetical vertical circular path of a particle suspended to that depth. The methods may further include varying the depth of the system as characteristics of the waves in the body of water change.

Description of Drawings

FIG. 1 is a depiction of an embodiment of a wave-energy converter and integrated inertial energy storage system deployed underwater.

FIG. 2 is a section across the band of the torus in FIG. 1 , that shows some of the interior components of the exemplary system.

FIG. 3 is a perspective drawing of the exemplary system of FIG. 1 that has been drawn to reveal some of the interior components.

FIG. 4 is depiction of the vertical orbits that hypothetical suspended particles travel along in the presence of surface waves.

FIG. 5 is a cross-section of the preferred embodiment of an exemplary magnetic levitation system.

FIG. 6 is an illustration of an exemplary corrugated flexible tube comprising segments that are flexible relative to each other.

FIG. 7 is an illustration showing how multiple instances of an embodiment of the system may be connected so that they share a single underwater cable.

FIG. 8 is a block diagram showing an exemplary method of how power could be generated and converted during startup of the system of FIG. 1.

FIG. 9 is a block diagram showing an exemplary method of how power could be generated and converted when wave energy is being harvested and used to both accelerate (or maintain the speed of) the rotatable ring of the system of FIG. 1 and to provide power to a grid or microgrid.

FIG. 10 is a block diagram showing an exemplary method of how power could be generated and converted when wave energy is being harvested to provide power to a grid or microgrid and when stored energy is also being retrieved to provide power to a grid or microgrid using the system of FIG. 1.

FIG. 11 is a block diagram showing an exemplary method of how power could be generated and converted when wave energy is being harvested and used to accelerate (or maintain the speed of) the rotatable ring and when energy from the grid is also being used to accelerate (or maintain the speed of) the rotatable ring.

FIG. 12 is a block diagram showing the power generation and conversion scenario of FIG. 10 but implemented with an alternative arrangement of AC/AC converters.

FIG 13. is a block diagram showing the power generation and conversion scenario of FIG. 9 but implemented with an alternative arrangement of AC/AC converters.

FIG. 14 is a block diagram showing the alternative configuration of FIG. 11 in a scenario where the Active Magnetic Linear Bearing controllers are powered from Emergency Power Storage because no other source of power is available.

FIG. 15 is a depiction of an additional embodiment of a wave-energy converter deployed underwater.

Detailed Description of the Invention

Disclosed herein are systems for generating electrical energy from wave energy. FIG. 1 illustrates one embodiment of such a system, the system 100. The system 100 is a combined wave-energy converter (WEC) and an inertial energy storage (IES) system. The system 100 may be deployed in a body of water that can propagate surface waves 101 such as an ocean or large lake. The system 100 may be anchored using at least one anchor line 102 to a sea floor or lake bed 103. The system 100 employs at least one anchor 105 to help affix the at least one anchor line 102 to a sea floor or lake bed 103. The system 100 may utilize at least one somewhat neutrally buoyant electrical cable 104 and at least one underwater cable 106 to deliver power to a grid or to receive power from a grid. There are several methods by which the energy generation output of the system 100 can be transported to where it is needed. The at least one somewhat neutrally buoyant electrical cable 104 can be attached between the system 100 and the sea floor 103 and also serve as an anchor. Thus, the somewhat neutrally buoyant electrical cable 104 can also be a dual purpose or multi- purpose cable. The at least one underwater cable 106 can be laid to transport power along the sea floor 103 to where it is needed. The at least one underwater cable 106 can also be a dual purpose or multi-purpose cable. A dual purpose or multi-purpose cable may include electric cables or communications mediums such as co-ax cables or fiber optics cables. It may include at least one pipeline for transferring fluids between the system 100 and a location at the other end of the cable. It may include at least one tube suitable for pneumatically transferring at least one capsule to and from the system 100 from elsewhere. A capsule could, for example, deliver a spare part to a robotic maintenance device 219 that operates within the system, or return (e.g. for inspection purposes) a sample of a lubricant that has been used by the system.

In the preferred embodiment (see FIG. 2), the system 100 is a large toroidally shaped apparatus, with at least one flexible outer shell 200 and with a hollow interior. It is designed to be immersed within a body of water, such as an ocean, that propagates energy in the form of surface waves.

The shape of a torus is defined by its diameter and by its bandwidth. If a pipe is bent into a circle and the ends joined to form a torus, the diameter of the pipe becomes the bandwidth of the torus, and the length of the pipe becomes the circumference of the torus. The diameter of the torus is the circumference of the torus divided by the number Pi.

A torus can be defined parametrically by:

c(b, f) = (R + r cos Q ) cos f

g(q, f) = (R + r cos Q ) sin f

z(q, f ) = r sin

where

q, f are angles which make a full circle,

R is the distance from the center of the tube to the center of the torus and is known as the“major radius,”

r is the radius of the tube and is known as the“minor radius,”

motion that causes a change in f is referred to as toroidal motion or motion in the toroidal direction, and

motion that causes a change in Q is referred to as poloidal motion or motion in the poloidal direction.

FIG. 2 shows a cutaway view of one side (that is, the left or right side) of the torus depicted in FIG. 1 and reveals the mechanisms within the torus. Within the torus there is at least one moving ring 201 (i.e. , rotatable ring) with a diameter like that of the torus, and at least one levitation system 202 (an example of a support structure) that can levitate, guide, accelerate, or decelerate the at least one moving ring 201. In FIG. 2 the direction of travel of the at least one moving ring 201 will be into or out of the page. Collectively the at least one moving ring 201 and the at least one levitation system 202 comprise an internal bracing mechanism. They also serve a second purpose as an inertial energy storage system.

When the at least one moving ring 201 is rotating at high speeds, tensile and inertial forces cause it to resist localized lateral displacements. The at least one levitation system 202 that is coupled to the at least one moving ring 201 , through the levitation technology, will likewise become resistant to localized lateral displacements.

The at least one levitation system 202 is coupled to the inner walls of the at least one flexible outer shell 200 through a plurality of power take-off units 203. A power take- off unit is designed to harvest mechanical energy so that it can be either converted into electrical energy or otherwise used to do useful work. Each power take-off unit 203 is biased towards resting at a mid-extension state to help keep the at least one levitation system 202 from drifting into contact with the at least one flexible outer shell 200.

At each end of each power take-off unit 203 there is at least one universal joint 217. At the point where a power take-off unit 203 attaches to the at least one levitation system 202, the at least one universal joint 217 at this attachment point is connected to at least one collar 218, and preferably said collar 218 encircles the at least one levitation system 202, is able to rotate around the at least one levitation system 202 in the poloidal direction, and is mechanically prevented from moving along the at least one levitation system 202 in the toroidal direction. Mechanical friction within the at least one universal joint 217 and the at least one collar 218 may be reduced by using bearings, lubricants, or other techniques well known in the art of designing mechanical systems.

When the at least one flexible outer shell 200 oscillates due to wave action, the oscillating motion is mechanically conducted to the plurality of power take-off units 203. As the plurality of power take-off units 203 are internally braced by the at least one levitation system 202 they will be actuated (for example, though extension or compression) and they will be able to harvest the mechanical power of their actuation.

The preferred embodiment can do the following: a) convert wave energy to electrical energy, b) use wave energy to increase the kinetic energy of the at least one moving ring 201 , and c) convert the kinetic energy of the at least one moving ring 201 into electricity.

In the preferred embodiment, mechanical components, such as the power take-off units 203 and levitation system 202, are housed within the at least one flexible outer shell 200 and are thus isolated from the marine environment. This enables these components to last longer and require less maintenance. Other marine hydrokinetic technologies use components, such as submerged turbines or pistons, that can leach lubricants into the marine environment through the seals around their shafts. This system does not depend on shafts that require watertight seals; therefore, it is able to avoid the problem of leaching lubricants.

Some wave energy technologies are reliant on establishing a secure anchorage point to the ocean floor (for example, by using tension anchors). However, the anchorage point can be costly to construct, and its construction can damage sea floor marine life. Furthermore, the need for secure anchorage limits the number of places where it is feasible to deploy the technology. In the preferred embodiment, the system does not require secure anchorage to the ocean floor, other than the possibility of using a small sea floor anchor to prevent the apparatus from drifting and to provide a path for electrical power to be delivered to land by way of an underwater cable.

The systems disclosed herein can be deployed far off-shore, and, as it is hidden underwater, it is not a scenic eyesore. Optionally, the depth of the systems disclosed herein can be actively adjusted to optimally match its wave energy harvesting capacity to the ambient wave energy density. Since wave energy density diminishes with increasing depth, the systems’ depth can be adjusted downwards (that is, deeper) when wave conditions are too energetic to avoid overextension and overcompression of the power take-off units. Device depth can be adjusted downwards, when needed, to avoid a collision with a ship or with ice. Similarly, when wave conditions are calmer, device depth can be adjusted upwards (that is, shallower) to increase extension and compression of the power take-off units to harvest more of each wave’s energy.

Referring again to the preferred embodiment, the system 100 comprises at least one flexible outer shell 200, at least one moving ring 201, at least one levitation system 202, and a plurality of power take-off units 203. A direction of movement of the at least one moving ring 201 is shown in FIG. 3 by the arrow labeled 304. The system 100 supports marine navigational aids 211 to help ensure that ships do not collide with it. It includes ballast material 212 to help it submerge when needed.

The at least one flexible outer shell 200 is designed to be flexible so that it can move with water 207 as surface waves 208 pass by. In the preferred embodiment, this flexibility is achieved using a corrugation technique, an example of which is depicted in FIG. 6. An example of a corrugation technique includes varying the minor radius of the torus with respect to the nominal minor radius in a sinusoidal manner as one moves in the toroidal direction. There are many methods of corrugation by creating a series of parallel ridges and furrows, and the system is not limited to any specific method of corrugation nor is it limited to any specific method of achieving flexibility or, for that matter, employing no special method other than to rely on the elasticity of the chosen material to achieve sufficient flexibility for the chosen geometry of the system. FIG. 2 depicts the cross-section of the material of at least one flexible outer shell 200, as well as the inner wall of the at least one flexible outer shell 205, which is visible in the figure because of the depiction of the use of corrugation of the at least one flexible outer shell. The use of corrugation or other method for increasing flexibility may be applied intermittently in the toroidal direction.

In the preferred embodiment, the radius of the particle orbit (that is, the vertical circular or elliptical path that is made by a hypothetical particle suspended in water as a surface wave 208 passes by) should be less than the minor radius of the torus. The particle orbit radius will decrease with increasing depth and will increase with increasing wavelength of surface waves 208. If surface waves 208 at a given time can be well characterized, the system 100 can be submerged to an optimal depth so that its minor radius is well matched to the particle orbit radius for that depth.

A section of the at least one flexible outer shell 200 resembles a pipeline segment. In the interest of clarity, terminology appropriate to pipeline segments will occasionally be used, especially when referring to a discrete section of the at least one flexible outer shell 200. The at least one flexible outer shell 200 must be made sufficiently flexible using one of many techniques known in the art of making flexible hoses.

These include, but are not limited to, using a flexible material, such as rubber, using a flexible material strengthened with circumferential or helical reinforcement rings or fibers, or using a less flexible material that is constructed with circumferential or helical corrugation to increase its longitudinal flexibility while maintaining its

circumferential strength. The pipeline can be constructed from alternating rigid sections and flexible joint sections provided that the flexible sections provide sufficient range of motion to make the composition sufficiently flexible. Joint sections can be made using any of the many techniques well known in the art of making flexible sealed joints.

Preferably, the pipeline has some axial flexibility, so that waves can cause sections of the at least one flexible outer shell 200 to move longitudinally (that is, in the toroidal direction) as well as transversely (perpendicular to the toroidal direction) relative to the internal bracing mechanism.

The at least one flexible outer shell 200 may be engineered so that it is able to flex without being crushed by water pressure at its rated operational depth. It should be noted that the interior 206 of the at least one flexible outer shell 200 may be pressurized or filled with an incompressible fluid, such as pure water, to help it resist the external pressure of the water within which it is submerged and to better match the buoyancy of the system to the buoyancy of the water that it is designed to be immersed in.

Ideally, the rated operational depth would be sufficient to allow the system 100 to avoid damage due to stormy weather conditions and to avoid collisions with ships that fail to heed navigational warnings. The preferred embodiment includes a depth control system that can: 1 ) detect that a ship in its vicinity is on an intercept course by using at least one passive sonar senor 214, 2) issue automated warnings to warn off the ship using at least one radio antenna 215 within or mounted on the at least one mast 209, and 3) should the oncoming ship fail to heed the warnings, submerge itself to a safe depth with sufficient rapidity to avoid a collision with the ship.

An exemplary method of depth adjustment involves measuring the depth and adjusting the buoyancy of the sections of the system 100 to affect a change in the depth such that, for all sections, the measured depth is brought into alignment with a desired setpoint depth. Depth measurement can be achieved using a plurality of water pressure sensors 213, a global positioning system 216 affixed to the at least one mast 209 that protrudes out of the water, sonar, optical sensors, or any of a number of techniques that are well known in the art. Control can likewise be implemented using an open loop or a closed loop controller, such as a P, PD, or PID controller or any of a number of control technologies well known to someone with skill in the art of control theory. Buoyancy adjustment can be achieved, for example, by: a) using a plurality of ballast tanks 212 to change the mass of a segment or segments of the at least one flexible outer shell 200 through the addition or removal of sea water or fresh water, b) changing the volume of a segment or segments of the at least one flexible outer shell 200 through a mechanical deformation of said shell segment, or c) a combination of (a) and (b). For example, said mechanical deformation may be achieved by expanding or contracting a corrugated section in the toroidal direction using hydraulic pistons. If the at least one mast 209 that protrudes out of the water is employed, the depth could be adjusted by applying an upward or downward force to at least one float 210 that is designed to travel up and down the at least one mast 209. That force could be applied using a plurality of electromagnets within the at least one mast 209 that act on ferrous material embedded within the float 210.

The depth adjustment techniques described above may also be used to maintain the system’s orientation with respect to the planet’s surface by countering gyroscopic effects that are inclined to prevent the ring from rotating along with the planet.

The at least one flexible outer shell 200 may be coated in or constructed from a material that is resistant to the corrosive effects of sea water and resistant to bio- fouling (for example, the accumulation of barnacles). In some embodiments, the at least one flexible outer shell 200 may be cleaned periodically. Additionally, the at least one flexible outer shell 200 is sealed so that the components within are isolated from the corrosive effects of the marine environment.

The at least one flexible outer shell 200 does not have to be toroidal in shape. A torus is just the most natural shape for enclosing the at least one moving ring 201 that, like a lasso, will prefer to assume a circular shape. Treating the at least one moving ring 201 as a loop of cable traveling within a pipeline, it is possible to constrain the path of the cable and make it assume any of a variety of shapes. For example: 1 ) the loop could be twisted into a“figure-eight,” 2) the loop could be could be squeezed into a more oval shape, 3) the loop could be the elongated shape of a chainsaw blade, or 4) the loop could be folded together so that there would be a“bi- directional” middle section with teardrop-shaped turnaround loops at each end.

The at least one flexible outer shell 200 can also be any shape that encloses the at least one levitation system 202 and the at least one moving ring 201. For example, it could be shaped like a ring, horn, or spindle torus; an oblate spheroid; or a biconcave disk with a flattened center.

Within the at least one flexible outer shell 200 there is a plurality of power take-off units 203. In the preferred embodiment, each power take-off unit 203 is attached to at least one point on the inner wall of the at least one flexible outer shell 200 and to at least one point on the at least one levitation system 202. These attachment points may be gimbaled to allow some range of motion in the axes represented by f and Q of a spherical coordinate system (not to be confused with the f and Q in the equation of a torus), with each gimbal centered around the origin of said spherical coordinate system.

The plurality of power take-off units 203 are spaced out longitudinally and

circumferentially and implemented in sufficient number to enable the at least one levitation system 202 to be supported and roughly centered within the interior of the at least one flexible outer shell 200.

In the preferred embodiment, a power take-off unit 203 may comprise a mechanical or hydraulic system that converts the linear motion of the power take-off unit’s 203 extension and compression into a more rapid rotation of a shaft that in turn drives an electric generator. For example, the power take-off unit 203 may be a hydraulic piston that pumps hydraulic fluid into an accumulator. The hydraulic fluid from the accumulator may drive a reverse hydraulic pump, which in turn may turn the shaft of an electric generator to produce AC current. Alternatively, the power take-off unit 203 may utilize a rack and pinion and potentially additional gearing to convert the linear motion of the power take-off unit’s 203 extension and compression into a more rapid rotation of a shaft that in turn may drive an electric generator. Alternatively, the power take-off unit 203 may utilize a toothed belt and pulley (and potentially other gears) to convert the linear motion of the power take-off unit’s 203 extension and compression into a more rapid rotation of a shaft that in turn may drive an electric generator. Alternatively, the power take-off unit 203 may utilize at least one strong permanent magnet that is forced past at least one electromagnet by the linear motion of the power take-off unit’s 203 extension and compression, such that an electric current is induced to flow within the coil of said electromagnet.

In the preferred embodiment, some or all of the plurality of power take-off units 203 are biased towards resting in a mid-extension state to help ensure that the at least one levitation system 202 remains roughly centered within the interior of the at least one flexible outer shell 200. The biasing may be entirely mechanical, entirely electrical, or, preferentially, a combination of both. Mechanical biasing, such as using springs, hydraulics, or pneumatics, is recommended for the biasing to offset static loads, such as supporting the weight of the at least one levitation system 202. A combination of active electrical biasing, supported by mechanical biasing, is recommended for dealing with the dynamic loads that occur when wave action causes the at least one flexible outer shell 200 to oscillate. The active electrical biasing may be a control circuit that determines how much electrical energy to harvest from the extension or compression of each power take-off unit. By electing to harvest more energy, the power take-off unit 203 will exert more resistance to extension or compression, and by electing to harvest less energy, the power take-off unit 203 will exert less resistance to extension or compression. In this way, the control algorithm can exert some control as to how much the at least one flexible outer shell 200 is influenced by the at least one levitation system 202 due to wave action. It can ensure that the at least one levitation system 202 never comes into direct contact with the inner walls of the at least one flexible outer shell 200. It can also ensure that the at least one moving ring 201 retains its shape.

To better comprehend the problem of retaining the shape of the at least one moving ring 201 consider the case where the moving ring 201 is, in fact, the shape of a ring. Put an observer in the center of the ring in a frame of reference that is rotating along with the ring, such that the at least one moving ring 201 appears stationary in the moving frame of reference. All of the other components are now spinning rapidly around the observer, from the observer’s point of view. The at least one moving ring 201 is under great tension due to inertial forces, so, like a piano string, it will have an innate tendency to resist being deformed. Wave forces imparted to the at least one flexible outer shell 200 and then to the least one levitation system 202 through the plurality of power take-off units 203 will be distributed around the least one moving ring 201. Forces imparted by one power take-off unit 203 will overlap with the forces imparted by many of the other power take-off units 203. Many of the imparted forces will be somewhat opposite forces and will somewhat cancel each other out. The control system can actively dampen any residual imparted forces and actively prevent the buildup of unwanted oscillations of the at least one moving ring 201. This can be done by actively controlling the amount of energy that each of the plurality of power take-off units 203 harvests. To achieve the oscillation dampening effect, the data from the plurality of position sensors (described later) is collected and centrally processed to identify and characterize the buildup of oscillations within the at least one moving ring 201. An appropriate dampening response (that is, a set of forces that, if applied, have the effect of dampening oscillations) can be computed. The required force adjustments can be rapidly communicated to the plurality of power take-off units 203 where they can be implemented using the active biasing method mentioned earlier.

If the at least one moving ring 201 comprises at least one ring moving with a first direction and speed, and at least one ring moving with a second direction and speed, then oscillations can be at least partially dampened by mechanically coupling the at least one levitation system of said rings using a mechanical dampening element, such as a shock absorber.

In the preferred embodiment, most of power take-off units 203 are designed to convert mechanical deformation directly into electricity; however, it is also anticipated that one or more power take-off units 203 may be employed to more directly do useful work. For example, a power take-off unit 203 could harvest the power of mechanical deformation to force salt water through a filter to produce fresh water, extract a mineral from sea water, pump sea water into or out of ballast tanks, pressurize a gas in a refrigeration system, or remove air from a compartment to generate a vacuum.

A power take-off unit 203 can also be used to pump a gas or a hydraulic fluid, and the flow of the gas or hydraulic fluid can then be used to generate electricity through a turbine or reverse hydraulic pump connected to a generator or fed to machines that do useful work when supplied with hydraulic or pneumatic power. In a hydraulic system a hydraulic accumulator may be employed to help ensure that the reverse hydraulic pump and electric generator receives a steady supply of hydraulic power.

It should be recognized that using electricity, pneumatics, and hydraulics are only three possible methods for transporting energy. Other methods, for example, using rotating or reciprocating shafts, belts, chains, or charging and transporting capacitors or batteries, are possible - although perhaps not as widely used in practice. The invention should not be construed and being limited to a subset of available technologies for transporting and making use of power.

The illustrated at least one levitation system 202 supports the at least one moving ring 201. In the preferred embodiment, the levitation system 202 employs active magnetic levitation that is biased with permanent magnets. A comparable technology is employed within active magnetic bearings or AMBs. These devices usually support a rotating shaft and allow it to rotate while preventing its position from deviating too much transversally and longitudinally (or axially). In the preferred embodiment, an Active Magnetic Linear Bearing (AMLB) is employed as part of the at least one levitation system 202. An AMLB allows its shaft to travel longitudinally (that is, in the toroidal direction for the circular embodiment disclosed herein) while preventing its position from deviating too much transversally. An AMLB may also be used to prevent the at least one moving ring from rotating in the poloidal direction. As the at least one moving ring 201 rotates toroidally, a discrete section of it can be viewed as a slightly bent shaft that travels longitudinally through a series of AMLBs. The AMLBs should preferentially be of a homopolar as opposed to a heteropolar design. In an AMLB the definitions of these terms differ from that of an AMB. An AMLB is engineered so that magnetic fields are homopolar in the axial direction (that is, the direction of motion of the moving ring) and heteropolar in the radial direction. This minimizes operational costs and heat generation because the longitudinally traveling moving ring will experience steadier magnetic fields, and steady fields do not induce currents within conductive components. Use of laminates and non- conductive materials where appropriate could also help prevent induced currents from being generated. Minimization of induced currents, such as eddy currents (aka Foucault currents), leads to: 1 ) less drag on the moving ring, 2) lower energy requirements for maintaining the ring’s rotational speed, 3) less waste heat generation, and 4) reduced thermal dissipation requirements.

While the steady magnetic fields will produce the forces needed to curve the path of the moving ring, Earnshaw's theorem explains that these permanent magnet fields are insufficient for stable levitation. The use of active electronics to precisely measure and maintain the specified separation of moving and stationary

components is favored within the magnetic bearing industry (Larsonneur, 2009). When biased with permanent magnets, the AMLBs will consume energy primarily when poorly anticipated disturbances perturb the system 100; therefore, the controlling components should be designed to anticipate the forces that are about to be exerted, and to be proactive in adjusting the position of the shaft (that is, a discrete segment of the at least one moving ring 201) within the magnetic field created by the permanent magnets of the AMLB. In this way the work done by the electromagnets can be minimized. Analogously, a passenger standing in a commuter train is not inherently stable within the Earth’s gravitational field - they will fall over if they do not actively maintain their balance. A passenger who is adept at anticipating when the car will start and stop accelerating will generally lean into the acceleration or deceleration in a timely manner, and thus will exert less effort to maintain balance.

In the preferred embodiment, the at least one moving ring 201 may be a loop of cable reinforced with industrial fiber that has high specific strength, such as carbon fiber. The cable can include a ferromagnetic material that the AMLBs interact with. In the preferred embodiment this ferromagnetic material may be a high electrical resistance material that is laminated or sintered to help reduce losses due to eddy currents. The industrial fiber should be oriented in the direction of motion of the at least one moving ring 201 and should be composed of very long strands, or, ideally, one continuous strand. The strands should be tensioned such that all strands bear an equal share of the tensile stress when the at least one moving ring 201 is in operation. The strands and the ferromagnetic material may be held together by using a binding compound.

A possible assembly technique is to: 1 ) assemble the industrial fiber and

ferromagnetic components, 2) impregnate the fibers with beads of the binding compound during assembly, 3) evacuate the air from the assemblage, 4) heat the components to a temperature that melts the binding compound, 5) compress the assemblage with externally applied forces to eliminate any voids within the material, and 6) allow the assemblage to cool. Variations of this technique are well known in the art of making fiber-reinforced composite parts. The at least one flexible outer shell 200 may be temporarily equipped with vacuum pumps, reinforced longitudinally, and may serve as the vessel that maintains the vacuum. The assembly, heating, compression, and cooling may be implemented using a combined assembly and autoclave machine that travels around the interior of the at least one flexible outer shell 200 and surrounds a portion of the at least one moving ring 201. Following construction of the at least one moving ring 201 the combined assembly and autoclave machine may be disassembled and removed. The at least one levitation system 202, the plurality of power take-off units 203, and other components may then be installed within the at least one flexible outer shell 200.

To enable construction and to provide access later for inspection, maintenance, and repairs, the at least one flexible outer shell 200 may be equipped with at least one sealable access hatch. This access hatch could be equipped with a docking port to enable a vessel to couple with it. This reduces the risk of water entering through the access hatch during maintenance operations and sinking the system.

In the preferred embodiment, the AMLBs use four sets of magnets positioned at 0,

90, 180, and 270 degrees around the shaft. It should be apparent to one skilled in the art that magnetic arrangements involving fewer than or more than four magnets are also possible, and that a magnetic levitation system can be made to function even if the magnets are not evenly spaced around the at least one moving ring 201. In the preferred embodiment, the rotation of the at least one moving ring 201

generates inertial forces that in turn create hoop stress within the at least one moving ring 201. This hoop stress is supported by the tensile strength of at least one moving ring 201. It is contemplated that in other possible embodiments that some or all of the inertial forces may be transferred through the AMLBs to the at least one levitation system 202. When this happens, some or all of the hoop stress in the at least one moving ring 201 will be transferred to the at least one levitation system 202. The at least one levitation system 202 must then be engineered to bear the

additional hoop stress.

The at least one levitation system 202 can store electrical energy as kinetic energy by accelerating the at least one moving ring 201. The at least one levitation system 202 can recover the electrical energy by decelerating the at least one moving ring

201

FIG. 5 shows a preferred embodiment of the at least one levitation system 202 in greater detail. The at least one levitation system 202 contains a plurality of

permanent biasing magnets 501 that create a plurality of magnetic fields 502 that penetrate the at least one moving ring 201. Coils of wire 504 can be electrically excited by the power amplifiers of the magnetic levitation system (not shown) to reinforce the plurality of any of the individual magnetic fields 502 within the plurality of magnetic fields 502 when needed to nudge the position of a portion of the at least one moving ring 201 into a more optimal position relative to the rest of the at least one levitation system 202.

While the use of a plurality of permanent biasing magnets 501 in the AMLBs is preferred, it is recognized that their use can increase manufacturing difficulty and cost. Their intended purpose is to reduce the power consumed by the AMLBs;

however, their use is not considered to be essential to the embodiments disclosed herein and should not be construed as being in any way limiting.

The position of the at least one moving ring 201 relative to the at least one levitation system 202 is measured by a plurality of position sensors. Position sensors, power amplifiers, and control theory are well known to people skilled in the art of designing AMBs, and with the benefit of this disclosure can be applied to the embodiments disclosed herein. Optionally, the coils of wire 504 also serve to provide positional data as described in Larsonneur (2009).

In the preferred embodiment, to accelerate and decelerate the at least one moving ring 201 , a slot 505 is made in the side of the at least one moving ring 201. A plurality of permanent magnets 506 are embedded into the walls of the slot 505. The strength and polarity of the magnetic field that is created by a plurality of permanent magnets 506 within the slot 505 is designed to change such that, if one were to move a magnetic field sensor within the slot 505 in the axial (or toroidal) direction (that is, into or out of the page in FIG. 5), one would observe the field changing in a sinusoidal manner as the at least one moving ring 201 rotates.

Within the slot 505 there is a plate 507 of material that is non-magnetic. The plate 507 supports a plurality of air coils 508 that are connected electrically to a plurality of electrical power converters 509. As the at least one moving ring 201 spins, the plurality of air coils 508 experience a sinusoidally varying magnetic field. The plurality of electrical power converters 509 can stimulate the plurality of air coils 508 with an alternating current to electrically induce a time-varying magnetic field that matches the frequency of the magnetic field created by the motion of the plurality of permanent magnets 506. By advancing the phase of said electrically induced magnetic field and sourcing power, the at least one moving ring 201 can be accelerated. By retarding the phase of said electrically induced magnetic field and sinking power, the at least one moving ring 201 can be decelerated. Components 505 through 509 comprise the motor/generator portion of the at least one levitation system 202.

The cavity within the at least one levitation system 202 may be evacuated to minimize the amount of air friction experienced by the at least one moving ring 201. While air coils 508 are preferred, these components do not have to be air coils but can in fact be any kind of electromagnet. For example, they could comprise a coil of wire 504 around a core made of laminated or sintered ferrous material. Introducing a ferromagnetic core within the air coil 508 would increase the magnetic force of said air coil 508 at the expense of increasing the amount of magnetic friction that the at least one moving ring 201 experiences. The sinusoidally varying magnetic field does not have to vary in a sinusoidal manner and may, in fact, be designed to vary in some other manner from the point of view of the air coil 508. For example, the field could be made to alternate between oscillating and non-oscillating states if the plurality of permanent magnets 506 within the slot 505 were installed intermittently in the toroidal direction. In an oscillating region, the sinusoidal variation does not have to be sinusoidal but could resemble a square wave, or triangle wave, or any other wave shape suitable for magnetically engaging the air coils 508 with the plurality of permanent magnets 506.

It should be apparent to one skilled in the art that the plurality of power take-off units 203 do not need to be perpendicular to the at least one levitation system 202 and that if they were angled this would allow a greater range of motion between the at least one levitation system 202 and the at least one flexible outer shell 200.

The system 100 can be anchored to the ocean floor to prevent it from drifting. By using a plurality of widely spaced anchors and by making the anchor line lengths adjustable, the system can be repositioned to avoid hazards such as drifting icebergs.

Slightly heavier than neutrally buoyant electrical cables 701 can be attached between multiple instances of the system 700a through 700e (e.g., multiple instances of the system 100) so that the multiple instances of the system 700a through 700e can share an underwater cable 702.

It is anticipated that the energy generation output of the disclosed systems can be used to generate a product that can be transported by transport vehicle or pipeline to where it is needed. For example, the system could power the process of hydrolysis to produce hydrogen gas. The electrical power could be used to run computer servers, and the incoming and outgoing information could be transported by fiber optic cable.

The system can be used to store energy generated elsewhere. For example, if the system were located near an off-shore wind farm, electrical energy produced by the wind farm could be stored within the at least one moving ring 201 , and then released to the grid at a later time. If the system is directly connected to the grid, it can provide the additional value of helping to manage the second-by-second fluctuations on the system as electrical machines and appliances are switched on and off, and as generators come on and off the system to meet the fluctuating demand.

While the preferred embodiment employs AMLBs, variations of the system that make use of other support structures for supporting the at least one moving ring 201 within the at least one levitation system 202 are contemplated. It should be understood by one with skill in the art, with the benefit of this disclosure, that passive magnetic bearings could be used in place of AMLBs, or non-magnetic bearings such as air- bearings or mechanical bearings (for example, ball bearings or roller bearings) could be used to meet different cost and performance requirements. It should also be understood by one skilled in the art that the at least one moving ring 201 within the at least one levitation system 202 together effectively comprise a rigid interior element that serves to brace the plurality of power take-off units 203. This rigid interior element could be a non-dynamic component if it were constructed with a sufficiently stiff material. Or, stated another way, the at least one moving ring 201 and the at least one levitation system 202 could be replaced by a non-rotating stationary ring operably connected to the plurality of power take-off units 203. For example, the rigid interior element could be constructed from a carbon fiber composite material.

Additionally, referring to FIG. 15, the rigid interior element could be a straight interior element 1501 if the at least one outer shell 1500 were also designed to be roughly linear in overall shape as opposed to roughly toroidal in shape. This straight interior element 1501 could be a sufficiently stiff rod or a cable that is designed to be stiffened by placing it under great tension. For example, it could be a cable that is stretched between two anchor points 1502. These anchor points 1502 could be, for example, two bases of a suspension bridge’s towers 1503, the two opposite shores of a channel or fiord 1504, two nearby islands, or a suitable combination such as the base of a tower and a point on shore. Said cable can also be anchored to the centers of the end caps 1505 of the roughly linear shaped at least one outer shell 1500. In this case, to generate tension on the cable, the at least one outer shell 1500 may be pressurized with a gas, such as air, or a fluid, such as fresh water.

FIG. 8 through FIG. 13 show a variety of operational states for the preferred embodiment disclosed herein.

Wave Excitation Forces are converted to Mechanical Energy and some of the Mechanical Energy is converted to electrical energy by Power Take-Off Units. The electrical energy produced by each Power Take-Off Unit is an alternating current (AC) and the amplitude and phase of the oscillations of this current are related to the displacement and rate of displacement of the Power Take-Off Unit that is generating the current.

FIG. 8 through FIG. 11 depict a first exemplary method wherein this Power Take-Off Unit generated AC current is converted to a second“rotatable ring rate” frequency of AC current by an AC to AC converter. The“rotatable ring rate” frequency is well matched to the frequency that is needed to electrically engage with motor/generators that accelerate and decelerate the at least one moving ring 201. The motor/generators are also represented by the air coils 508, permanent magnets 506, and electrical power converter 509 of the at least one levitation system 202. AC current at the rotatable ring rate is converted to a third“Grid Frequency” frequency of AC current by an AC to AC converter.

FIG. 12 and FIG. 13 depict a second exemplary method wherein the power take-off unit generated AC current is instead converted to a third“Grid Frequency” frequency of AC current by an AC to AC converter. The Grid Frequency current is then converted to the rotatable ring rate current by using another AC to AC converter.

This embodiment may have less overall AC to AC conversion efficiency loss if most of the harvested wave energy is delivered directly to the grid, and less of the harvested wave energy is transferred to the at least one levitation system 202.

In either the first or second exemplary methods, the rotatable ring rate current is distributed to the plurality of air coils 508 of the at least one levitation system 202 that are responsible for accelerating and decelerating the at least one moving ring 201. When said ring is accelerated (as shown in FIG. 8, FIG. 9, and FIG. 11 ) the Motor Generators will sink power. When said ring is decelerated (as shown in FIG.

10, and FIG. 12) the Motor Generators will source power.

It is also contemplated that with the addition of switches that allow the arrangement of AC to AC converters to be altered, a system could be reconfigured on the fly to support either the first or second exemplary methods, and that such reconfiguration could be done to optimize system performance based on the current sea state, demand for energy, speed of the at least one moving ring 201 , and potentially other factors.

AC current at the grid frequency may be passed through a step-up transformer, an underwater cable, and then a step-down transformer to connect it to a grid or microgrid. These components are optional but are often used to reduce losses when AC power is transferred over long distances. Other techniques, known to people experienced in the art, such as the use of AC to DC converters, DC to AC converters, and high-voltage DC for the current that travels through the underwater cable, may also be employed.

AC current at the grid frequency may also be converted to DC power and supplied to an emergency power storage system and to the Active Magnetic Linear Bearing controllers. This DC power may be used to power the circuits that control the levitation of at least one moving ring 201. FIG. 8 depicts an exemplary flow of power in the preferred embodiment during startup. In this case, power is supplied from the grid to the system. The power is used to levitate and accelerate the at least one moving ring 201 , and to charge the emergency power storage component.

FIG. 9 depicts an exemplary flow of power in the preferred embodiment when it is harvesting wave energy, supplying some of the harvested energy to the grid, supplying some of the energy to the AMLB controllers, and supplying some of the energy to the motor/generator controllers.

FIG. 10 depicts an exemplary flow of power in the preferred embodiment when it is both harvesting wave energy and sourcing energy stored in the at least one moving ring 201 by using the Motor/Generator controllers. Some of this energy is supplied to the grid and some of the energy is supplied to the AMLB controllers and Emergency Power Storage.

FIG. 11 depicts an exemplary flow of power in the preferred embodiment when it is both harvesting wave energy and sourcing energy from the grid. Some of this energy is stored in the at least one moving ring 201 by using the Motor/Generator controllers, and some of this energy is supplied to the AMLB controllers and Emergency Power Storage.

FIG. 12 depicts an exemplary flow of power in the preferred embodiment when it is both harvesting wave energy and sourcing energy stored in the at least one moving ring 201 by using the Motor/Generator controllers. Some of this energy is supplied to the grid, and some of this energy is supplied to the Active Magnetic Linear Bearing controllers and Emergency Power Storage. In this case the AC from the power take- off units 203 is converted directly to AC at the grid frequency and AC at the rotatable ring rate is also converted directly to AC at the grid rate. The conversions are more direct for the scenario than those of the system depicted in FIG. 10.

FIG. 13 depicts an exemplary flow of power in the preferred embodiment when it is both harvesting wave energy, supplying some of the harvested energy to the grid, supplying some of the energy to the AMLB controllers, and supplying some of the energy to the Motor/Generator controllers. If most of the generated energy is supplied to the grid, then conversions depicted here are more direct for the scenario than those of the system depicted in FIG. 9.

FIG. 14 depicts an exemplary flow of power in the preferred embodiment when it is not harvesting wave energy, sourcing energy stored in the at least one moving ring 201 by using the Motor/Generator controllers, or sourcing energy from the grid. In this case, energy is supplied to the AMLB controllers from the Emergency Power Storage.

The system’s depth control systems may be coupled to a system that is designed to detect seismic events and anticipate tidal waves. Should a tidal wave be detected that could damage the system, the system could, if deemed necessary, execute an emergency shutdown to avoid being damaged as the tidal wave passes by.

The phrases“operably connected to” and“connected to” refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluidic, and thermal interaction. Two entities may interact with each other even though they are not in direct contact with each other. For example, two entities may interact with each other indirectly through an intermediate entity.

One of skill in the art, with the benefit of this disclosure, would understand that the systems and methods disclosed herein may also include other components and method steps. The examples and embodiments disclosed herein are to be construed as merely illustrative and exemplary and not a limitation of the scope of the present disclosure in any way. It will be apparent to those having skill in the art, and having the benefit of this disclosure, that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the disclosure herein.

References

Larsonneur, R. (2009). Principal of Active Magnetic Suspension. In G. S. Maslen, Magnetic Bearings (p. 27).

Claims

1. A system for converting wave energy to electrical energy and other useful forms of work, the system comprising:

an outer shell configured to be suspended in a body of water and configured to move with waves in the body of water;

a rigid interior element located at least partially within the outer shell and configured to resist movement with waves in the body of water; and

a power take-off unit operably connected to an inside of the outer shell and operably connected to the rigid interior element, wherein the power take-off unit converts motion of the outer shell relative to the rigid interior element into electrical energy or applies mechanical work to another system.

2. The system of claim 1 , wherein the rigid interior element comprises a ring located entirely within the outer shell.

3. The system of claim 2, wherein the ring comprises a rotatable ring configured to continuously rotate within the outer shell during operation and thereby resist lateral movement as the outer shell is moved by waves in the body of water.

4. The system of claim 3, further comprising a support structure configured to support the rotatable ring and operably connected to the power take-off unit.

5. The system of claim 4, wherein the support structure comprises a levitation system that utilizes magnetic forces to levitate the rotatable ring.

6. The system of claim 5, wherein the levitation system is configured to use electrical energy to increase the rate of rotation of the rotatable ring.

7. The system of claim 6, wherein the levitation system is configured to convert kinetic energy of the rotatable ring into electrical energy.

8. The system of claim 2, wherein the ring comprises a stationary ring and a plurality of power take-off units that are operably connected to said stationary ring in opposition to each other and thereby resist lateral movement as the outer shell is moved by waves in the body of water.

9. The system of claim 2, further comprising an anchor and a cable attached to the outer shell and independent of the ring.

10. The system of claim 1 , wherein the rigid interior element comprises a cable or rod.

11. The system of claim 10, wherein the cable or rod is operably connected to two anchor points and placed under tension to thereby resist lateral movement as the outer shell is moved by waves in the body of water.

12. The system of claim 11 , wherein the outer shell circumscribes all or a portion of the cable or rod.

13. The system of claim 1 , wherein all moving parts used to convert mechanical energy to electrical energy are contained within the outer shell and are isolated from the body of water during operation.

14. The system of claim 1 , wherein the outer shell comprises segments that are flexible relative to each other, wherein a first portion of the outer shell is capable of moving in one direction and a second portion of the outer shell is capable of moving in a different direction as the outer shell is moved by waves in the body of water.

15. The system of claim 1 , wherein the outer shell has a circular cross-section.

16. The system of claim 1 , wherein the power take-off unit comprises a generator for converting linear mechanical energy into electrical energy.

17. The system of claim 1 , further comprising a plurality of power take-off units operably connected to a support structure for the rigid interior element, wherein the plurality of power take-off units are juxtaposed relative to each other and are each operably connected to the inside of the outer shell.

18. The system of claim 17, wherein the rigid interior element comprises a ring and the outer shell is toroidally shaped.

19. The system of claim 1 , further comprising a dual purpose cable that contains at least one insulated wire operably connected to the power take-off unit and configured to carry power away from the system and that also serves to anchor the system within the body of water.

20. The system of claim 1 , further comprising a depth control system that can vary the depth of the outer shell.

21. A method of making the system of claim 2 from fibers, the method comprising: using a combined assembly and autoclave machine that travels around the interior of the outer shell and sequentially surrounds a portion of the ring, until the ring is formed within the outer shell;

disassembly and removal of the combined assembly and autoclave machine; and

installation of the power take-off unit.

22. A method of generating electricity or other useful forms of work from waves, the method comprising: characterizing the wavelength of waves in a body of water; and deploying the system of claim 1 in the body of water to a depth where the maximum radius of the outer shell is greater than a hypothetical vertical circular path of a particle suspended to that depth.

23. The method of claim 22, varying the depth of the system as characteristics of the waves in the body of water change.