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WO2017015626A1 - Convertisseur d'énergie des vagues amélioré - Google Patents

Convertisseur d'énergie des vagues amélioré Download PDF

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Publication number
WO2017015626A1
WO2017015626A1 PCT/US2016/043721 US2016043721W WO2017015626A1 WO 2017015626 A1 WO2017015626 A1 WO 2017015626A1 US 2016043721 W US2016043721 W US 2016043721W WO 2017015626 A1 WO2017015626 A1 WO 2017015626A1
Authority
WO
WIPO (PCT)
Prior art keywords
surface float
reaction plate
wave energy
energy converter
linear
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2016/043721
Other languages
English (en)
Inventor
Timothy R. MUNDON
Balakrishnan G. Nair
Jennifer VINING
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oscilla Power Inc
Original Assignee
Oscilla Power Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oscilla Power Inc filed Critical Oscilla Power Inc
Priority to GB1802807.6A priority Critical patent/GB2557501B/en
Priority claimed from US15/217,772 external-priority patent/US10393089B2/en
Publication of WO2017015626A1 publication Critical patent/WO2017015626A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • F03B13/18—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore
    • F03B13/1845—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore and the wom slides relative to the rem
    • F03B13/1865—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore and the wom slides relative to the rem where the connection between wom and conversion system takes tension only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B9/00—Water-power plants; Layout, construction or equipment, methods of, or apparatus for, making same
    • E02B9/08—Tide or wave power plants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • F03B13/20—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" wherein both members, i.e. wom and rem are movable relative to the sea bed or shore
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
    • H02N2/18—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing electrical output from mechanical input, e.g. generators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2220/00—Application
    • F05B2220/70—Application in combination with
    • F05B2220/706—Application in combination with an electrical generator
    • F05B2220/707—Application in combination with an electrical generator of the linear type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2250/00—Geometry
    • F05B2250/70—Shape
    • F05B2250/73—Shape asymmetric
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/02—Transport, e.g. specific adaptations or devices for conveyance
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/40—Transmission of power
    • F05B2260/406—Transmission of power through hydraulic systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient

Definitions

  • the wave energy converter includes a surface float including a non-axisymmetric profile, a reaction plate configured to be submerged below a water surface, and more than one flexible tether, each mechanically coupled to both the surface float and the reaction plate, the reaction plate having a moment of inertia in pitch and roll greater than a moment of inertia in pitch and roll of the surface float.
  • the surface float is designed to move in heave, pitch and roll, but with different natural periods for at least two of these three motions, such that these natural periods will be distributed across the significant period range where the cumulative wave energy content for the deployment location.
  • the surface float has a load transfer unit for each tether to enable forces to be efficiently transmitted to the linear hydraulic gearbox, eliminating any off-axis loads.
  • the reaction plate has a geometry that provides asymmetric hydrodynamic forces in the up and down directions.
  • at least one tether is mechanically coupled to at least one linear hydraulic gearbox.
  • At least one linear hydraulic gearbox is mechanically coupled to at least one linear generator.
  • the linear hydraulic gearbox includes at least one piston that has a first area, and another piston that has a second area, where the first and second areas are not the same.
  • the linear hydraulic gearbox employs at least one set of tandem cylinders.
  • the linear hydraulic gearbox can amplify the displacement and speed of a translator in at least one linear generator relative to the displacement of the surface float relative to the reaction plate.
  • the surface float and reaction plate have geometries that allow these to be mated together during transportation.
  • the method includes operating a wave energy convertor device that includes a surface float including a non-axisymmetric profile and a powertrain, a reaction plate configured to be submerged below a water surface, and more than one flexible tether, each mechanically coupled to both the surface float and the reaction plate, the reaction plate having a moment of inertia in pitch and roll greater than a moment of inertia in pitch and roll of the surface float.
  • the method further includes facilitating motion of the surface float relative to the reaction plate, capturing at least some energy from waves, and transmitting the at least some energy to a powertrain in the surface float via at least one of the more than one flexible tether.
  • Other embodiments of methods for capturing and converting mechanical energy from ocean waves are also described.
  • Fig. 1 depicts an embodiment of a wave energy converter including a surface float with a non-axisymmetric profile, a reaction plate, and flexible tethers.
  • Fig. 2 depicts one embodiment of the wave energy converter of Fig. 1 with the surface float partially transparent to show internal components.
  • Fig. 3 depicts one embodiment of a side view of the wave energy converter of
  • Fig. 4 depicts one embodiment of a rear view of the wave energy converter of
  • Fig. 5 depicts one embodiment of an isometric view of the surface float.
  • Fig. 6 depicts one embodiment of a top view of the wave energy converter of
  • FIG. 7 depicts a schematic diagram of a farm or array of wave energy converters
  • Fig. 8 depicts motions of the surface float.
  • FIG. 9 depicts an embodiment of a simplified hydraulic arrangement that shows the use of tandem cylinders to change load amplification ratios.
  • Fig. 10 depicts an embodiment of an array of magnets in a linear generator configured to move within a coil array.
  • Fig. 11 depicts flux paths of adjacent magnets from a finite element simulation.
  • Fig. 12 depicts a schematic diagram of an embodiment of a magnetic circuit.
  • Fig. 13 depicts schematic diagram of an embodiment of an electrical layout.
  • Fig. 14 depicts an embodiment of a structural layout and overall shape of a hull structure of a surface float with internal components.
  • Fig. 15 depicts one embodiment of a load transfer unit.
  • Fig. 16 depicts one embodiment of a heave plate retracted and mated with a surface float.
  • Fig. 17 depicts another embodiment of a heave plate retracted and mated with a surface float.
  • Heave plates have been used extensively in the offshore space in order to damp the heave response of a body in a wave environment.
  • the principle of operation is that the large plates, which are disposed such that their largest projected area is in a plane that is perpendicular to the heave direction, are attached below the surface of the water to limit (e.g., delay, dampen, decrease, etc.) motion in the heave direction.
  • This increases the added mass of the system by adding a considerable drag force to the system at the location of the plate.
  • the water around the plate must also be accelerated.
  • the area and configuration of the plate are designed in order to optimize this increase in added mass.
  • the heave plate is also generally disposed at a depth where the motion of the waves is much more attenuated than at the surface.
  • Embodiments of the invention described herein relate to an advanced wave energy converter 100 design (Figure 1) that employs a number of innovative features/subsystems, described below, that in some combinations will deliver a high Annual Climate Capture Width (ACCW) with low characteristic Capital Expenditure (CAPEX). These features/sub- systems are:
  • Some embodiments of this invention may employ a system design with multiple modes of energy capture.
  • Some embodiments of the new wave energy converter 100 can be conceptualized as point absorbers with additional modes of motion allowing energy capture from waves in pitch and roll as well as heave.
  • Some embodiments of the device may have a surface float 102 shaped to maximize or emphasize energy capture in the dominant wave direction, and designed to move in heave, pitch and roll, but with different natural periods for each of these motions. In some embodiments, the natural periods of at least two of these three motions will be distributed across the significant period range where the cumulative wave energy content for the target deployment location is concentrated, resulting in a highly efficient wide-band energy capture across the across the wave spectrum, and increasing the ACCW of the system.
  • the geometry of the surface float 102 is designed to maximize or influence roll and pitch response and operate as a good wave radiator and hence a good wave absorber.
  • this invention may comprise a reaction plate 104, or a heave plate, mechanically coupled to the drivetrain on the surface float using non-rigid or flexible tethers 106.
  • the heave plate 104 may have at least one property or characteristic that is asymmetric in the vertical direction (i.e., the direction of gravitational force), and this property or characteristic may be, without limitation, drag force or added mass.
  • multiple modes of motion are enabled by the use of three or more flexible tethers 106 that connect the surface float 102 to the heave plate 104. In some embodiments, this enables the heave plate 104 to be located at sufficient depth to reduce or minimize wave forces applied to the heave plate 104, and provide substantial or maximum reaction force, without incurring prohibitive structural cost.
  • the heave plate 104 is designed to provide maximum or concentrated reaction forces in heave (mass, drag) as well as pitch/roll (high relative moment of inertia) the vertically asymmetric geometric profile enables slack/snap loads in the tethers 106 to be eliminated even under very high waves. In some embodiments, this enables low-cost deployment operations by mating with the surface float 102, allowing tow to site by non- specialist vessels. In some embodiments, this allows for a survival mode strategy by retracting the heave plate fully, mating with the surface float (see e.g. , Figures 16 and 17) and essentially functioning as a one-body wave follower under extreme waves.
  • each tether 106 is connected directly to a linear drivetrain 108 located in the surface float 102.
  • this linear drivetrain 108 comprises at least one linear hydraulic gearbox and at least one linear generator, designed such that the velocity input to at least one linear generator is amplified by an amplification ratio relative to the motion of the surface float 102.
  • this amplification ratio can be adjusted remotely to match the current sea-state, so that the generators can operate at relatively high (e.g., 50% of maximum or higher, 75% of maximum or higher, or 90% of maximum or higher) or maximum efficiency and with high reliability.
  • a variety of strategies can be adopted to control damping to increase capture efficiency.
  • Some embodiments of this invention may be manufactured at a CAPEX low enough to enable usage and adoption for utility scale power generation.
  • a low cost structure is possible due to: (1) low structural mass requirements due to the employment of flexible tethers 106; (2) small generator size/mass requirements due to displacement amplification; (3) no requirements to store and pump hydraulic fluid; embodiments of the system operate essentially as a hydrostatic system; (4) Hydraulic components that require little modification from catalog items from established vendors; (5) generators suitable for high volume manufacturing; (6) system mass being dominated by low cost materials such as steel (float) and concrete (heave plate); (7) design capable of tow-to-site deployment with non- specialized vessels.
  • Embodiments of the invention relate to a multi-mode point absorber that captures energy in pitch, heave and roll, (see e.g. , Figure 8) and to methods of using and operating such a device.
  • Some embodiments may comprise a surface float 102 that has dynamic characteristics that adjust or maximize motions in heave, pitch and roll at different natural frequencies that are distributed in order to improve (compared with static
  • the linear hydraulic gearbox converts this mechanical energy into a higher displacement, lower force mechanical energy, which is directly applied to linear generators with minimal energy loss (>95% efficiency).
  • the displacement amplification ratio may range from 0.5 to 100. In some embodiments, the displacement amplification ratio may range from 1.5 to 20, and more specifically from 2 to 8.
  • the linear hydraulic gearbox has a displacement amplification ratio of 4, enabling an 8m linear generator stroke to be achieved internal to the surface float (500 kN/8 m per linear powertrain).
  • the linear generator is able to convert this mechanical energy into electrical energy with very high efficiency (>85% typical).
  • Some embodiments may employ methods for tuning the generator damping by employing machine configurations that allow for advanced control topologies whereby force and/or VAR support can be controlled for relatively high or maximum conversion efficiency.
  • the power electronics sub-system further conditions the output and converts it to a smooth, high-voltage DC output at high efficiency (>97% expected) to be delivered it to the grid through a High Voltage subsea transmission lines.
  • Figures 2-6 depict an embodiment of geometry of the surface float 102 in three orthogonal planes and one three-dimensional perspective.
  • Figure 4 shows one embodiment of the float in the water (shown to be still for the sake of clarity).
  • the geometry of the surface float 102 is intended to make the system more conducive to pitch and roll.
  • the non-axisymmetric profile is designed to radiate waves predominantly in the direction of its key axis when pitching, with the expectation that this will result in higher efficiency wave capture due to a reduction in radiated waves perpendicular to the incident wave direction.
  • the mass properties of the surface float 102 may be designed to have a particular ratio relative to that of the heave plate 104.
  • Tuning the ratio of moment of inertia (Mo I) between these two structures is implemented for system resonance in a particular mode of motion. Additionally, the response in these rotational (and heave) modes may be tuned by adjusting the mass properties of the surface float through the addition of water ballast.
  • Some embodiments are directional and designed to optimize energy capture from a particular direction. Some embodiments may be designed to be non-directional and designed to orient themselves in the direction of the dominant wave. In the majority of cases, especially on the US west coast, wave directionality is confined to a small range of directions. Depending upon the incident wave direction, the device response will change, and maximum efficiency will occur when the incident wave direction coincides with the device primary axis (either in the +ve or -ve direction). The effect of off-axis waves will be only a small reduction in efficiency (e.g., less than 5%, less than 10%, or less than 25%) and will not have any impact upon the structural integrity of the device.
  • the mooring connection will be made to the surface float with a standard three point mooring, with surface floats on the mooring lines providing horizontal compliance.
  • anchor points will be shared between devices to reduce the costs of anchor installation and infrastructure costs.
  • the farm 700 will be laid out in a staggered grid with the grid normal to the primary or dominant wave direction.
  • devices will be arranged to use common anchor points to reduce configuration costs.
  • the mooring configuration and water depth will determine the specific separation between devices.
  • each device would have its own subsea cable to shore.
  • individual devices would be connected into a common bus system with wet matable, dynamic cable connections to the sea floor.
  • each wave energy converter will have a separate dynamic electrical cable to the sea floor.
  • electrical cables may include fiber for communications.
  • electrical cable buses will be aggregated in a substation that will be either a floating platform or a subsea unit.
  • device separation would be adequate to allow access of moderate sized support vessels between device moorings.
  • the installation & recovery methodology of the system would allow a small vessel with onboard hydraulics to recover the heave plate for a single device and either perform a full range of maintenance operations, or disconnect the moorings and tow the device out of the farm 700 and to port for major overhaul.
  • individual device operating parameters would be controlled at a farm level, with wave states being advised by wave measurement buoy(s) on the perimeter of the array. In some embodiments, wave state across the array will be used to advise generator damping and to advise entry of survival configuration.
  • the load and power flow paths for the primary power absorption step are:
  • the elongated shape of the surface float 102 of the wave energy converter may be designed to have different natural periods in heave, pitch and roll.
  • the range of natural periods in two or more modes may span the significant period range where the cumulative wave energy content for the deployment location is concentrated (e.g. 6-12 s periods for the US West Coast), resulting in highly efficient wide-band energy capture across the wave spectrum, and increasing the ACCW.
  • the two-dimensional theoretical efficiency is 100% in regular waves as the float can move and capture energy in heave, pitch and roll (practical efficiency in three-dimensional irregular waves is much lower).
  • the heave period primarily depends upon the system mass, buoyancy and damping, but is also influenced by the damping characteristics of the powertrain.
  • the roll and pitch periods are changed by altering their respective radii of gyration (k, which in turn may be increased by increasing the second moment of area for the particular motion and decreasing the total cross-sectional area) relative to that of the heave plate, about the relevant axis through the center of gravity and by decreasing the stability index (GM, is the spacing between metacenter and the center of gravity).
  • GM is the spacing between metacenter and the center of gravity.
  • the roll and pitch periods can be adjusted by float design and mass distribution to change the radius of gyration for the particular motion and/or the metacenter, or by float weight distribution and ballasting to affect the center of gravity.
  • Materials that may be used include— Surface Float: Steel; Tethers: Synthetic ropes (Spectra, Polyester); Heave Plate: Steel reinforced concrete; load transfer unit (LTU): Steel and seawater lubricated bearing material (Delryn or similar). It is to be noted here that there are many alternative materials that may be used for each of the sub-systems noted above, and the choice of a particular material in no way limits the scope of this invention.
  • the surface float may have a load transfer unit (LTU) (see e.g., Figure 15) on each tether to enable forces to be efficiently transmitted to the linear hydraulic gearbox, eliminating any off-axis loads. Consequently, the LTU effectively acts as a linear bearing and is thus subject to horizontal and rotational loads.
  • the hull will be subject to constant hydrostatic pressure, and a variety of intermittent forces due to wave slamming.
  • end-stops are needed and will be integrated into the structure of the LTU.
  • motions in higher/extreme waves will be limited in other ways (e.g. effective use of the hydraulic return springs) so that the end-stops will rarely, and ideally, never be engaged.
  • the properties/characteristics of the device may be tuned to control energy capture.
  • system natural periods are designed into the device as discussed above, although adjusting the system mass by adjusting the ballast and/or the linear drivetrain displacement will allow some degree of fine tuning.
  • Some embodiments of this invention may employ an asymmetric reaction-plate (or heave plate).
  • the heave plate is designed with a high moment of inertia relative to the surface float in both the pitch and roll directions, to provide relatively high or maximum reaction force.
  • its geometry provides asymmetric
  • the asymmetric geometry may significantly reduce the likelihood of slack tether events occurring in extreme waves.
  • a secondary power conversion step is a mechanical power-conditioning step with a linear hydraulic gearbox that has the following
  • the primary hydraulic system operates in a nearly hydrostatic configuration with two pistons whose areas are designed such that there is an amplification of the displacement of one cylinder relative to the other at the cost of reduced force.
  • This operation is somewhat analogous to that performed by a rotary gearbox, which converts input rotary energy at one RPM into a different (usually higher) RPM that is more suitable for optimal performance of a rotary generator.
  • the simple, nearly hydrostatic operation of the hydraulic gearbox is similar to that used in a hydraulic press, in which a compressive force on one cylinder is transferred directly to another cylinder with a different piston area, resulting in an amplification ratio that is dependent upon the ratio of the piston areas.
  • this ratio can be adjusted during operation.
  • a number of innovative control schemes can be used. Since the operation is nearly hydrostatic, the power transfer efficiency is extremely high (>97% assumed). At the frequencies of interest (say for periods longer than 4 seconds) the hydraulic losses are minimal.
  • the hydraulic system utilizes tandem cylinders and valves which can be controlled remotely to adjust system amplification ratios as shown in Figure 9.
  • the system will be tuned to operate at very high efficiency by increasing or maximizing PTO displacement. As input energy increases, this system displacement can be reduced to lower the effective system efficiency, limiting power capture and hence limiting system loads under high external wave forces.
  • Typical materials that may be used include: Cylinders: High strength steel; Piston Rods: High strength steel; Working fluid: Hydraulic oil. It is to be noted here that there are many alternative materials that may be used for each of the sub-systems noted above, and the choice of a particular material in no way limits the scope of this invention.
  • the hydraulic system is similar to hydraulic presses that are designed to hundreds of millions of load cycles routinely in industrial applications. If one of the hydraulic systems experiences minor malfunctions, the effect on the system will be a derating and not loss of use.
  • the force applied by the tethers may be utilized in different ways.
  • the force applied by the tethers may be used to pump a fluid such as, without limitation, air, water or hydraulic fluid and increase the pressure and/or volume of the fluid stored and effectively store energy in the form of pressurized hydraulic fluid.
  • This pressurized fluid can then be released as desired to drive a rotary or linear generator either in the device itself or external to the device (e.g. pumped to shore to drive an electric generator).
  • the force applied by the tethers may be conditioned by some other mechanical means including, without limitation, levers or pulleys to increase either the force or displacement that is applied on an electric generator.
  • the displacement may be amplified using a variety of means including, without limitation, levers or pulleys and used to drive a linear generator.
  • the force using a variety of means including, without limitation, levers or pulleys and used to drive a variable reluctance generator, such as a magneto strictive generator.
  • Some embodiments of this invention include any and all combinations of hydraulic and mechanical means to amplify either load or displacement so as to drive any type of electrical generator including, without limitation, linear generators, rotary generators, gas/fluid turbines or variable reluctance generators, including magneto strictive generators.
  • a simplified Hydraulic arrangement 900 is depicted that shows the use of tandem cylinders to be able to change the load amplification ratios.
  • the cylinder selection shown indicates a reduction in displacement, and increase in force, but by changing the cylinder ratios with the same arrangement would apply equally to the described system whereby the displacement will be increased. Also note only the compressive side of the secondary hydraulic piping is shown for simplicity.
  • each of the linear hydraulic gearboxes couples with a linear generator, designed to provide rated power at a displacement/speed higher than the wave induced motion of the surface float.
  • the generator size and weight for delivering rated power can be substantially reduced due to the amplified speed of the translator. This creates a size reduction that allows the combined system to be comfortably located inside the surface float, reducing CAPEX, and allowing easier installation, limited limitations on manufacturing and lower O&M costs due to much easier access during maintenance operations.
  • the linear generator may consist of an array 1010 of magnets configured to move within a coil array as shown in Figure 10.
  • the disc-shaped magnets may be axially magnetized with a central bore, which allows mounting onto a core rod.
  • the magnets may be oriented such that adjacent magnets have opposite magnetic polarizations.
  • Opposing magnets may be separated using magnetically permeable (e.g. made of mild steel or electrical steel laminations) - spacers that have the same radial geometry and dimensions as the magnets themselves.
  • the flux paths 1100 of adjacent magnets from a finite element simulation are shown in Figure 11 and a schematic diagram 1200 of an equivalent magnetic circuit is shown in Figure 12.
  • the stators are designed with slots to house the copper coils, and the smallest inner diameter of the stator rings are configured such that they have a clearance with the magnets/spacers that defines a ring shaped air gap within the flux path.
  • the flux from each magnet north pole is directed back to its own south pole through the spacer, the air gap and the stator.
  • the non-magnetic core rod forms a weak competing flux path, and some leakage flux flows through the core rod.
  • the flux coupling through the stators and spacers will be maximized when the magnets are located completely inside the coils, and will be zero when they are completely outside of the coils.
  • Preliminary sizing estimates show a total of 14 metric tons of active mass per generator (this includes the main shaft of the translator).
  • a three-phase (or other multiphase) machine allows for advanced control topologies whereby force and/or VAR support can be controlled to adjust or maximum conversion efficiency.
  • a control strategy that varies the electrical load on a generator for precision impedance matching will be used.
  • Machine efficiency is a function of control method
  • the overall efficiency of the electrical power conversion is estimated to be greater than 85%.
  • a linear generator must accommodate significant forces on the shaft bearings due to the air gap flux.
  • embodiment is a design with bearings in the air gap that not only control and determine the size of the air gap, but provide support to the central shaft so that its diameter can be significantly smaller than is possible with support only at the edges.
  • the load distribution on the bearing can also help to mitigate the impact of deflections/vibrational loads caused by cogging forces.
  • power shedding can be accommodated by the power electronics system by changing the generator damping to limit efficiency.
  • force limits can be imposed by controlling the reactive force through three-phase control.
  • the generator has no intrinsic displacement limits, but will share end-stops with the linear hydraulic gearbox. Inherent redundancy comes from multiple generators and multiple windings on each generator in parallel circuits. Minor electrical failures will result in system de-rating and not down-time.
  • the system will deliver power with voltage and power quality compliant with grid codes and similar to other renewable sources such as offshore wind. Referring to Figure 13, a schematic diagram 1300 of an embodiment of an electrical layout is depicted.
  • the surface float is primarily composed of a steel hull structure manufactured analogously to a typical barge or boat. It may include a steel superstructure with a plated steel hull around this to provide buoyancy. In some embodiments,
  • the generators may be located longitudinally inside the hull on a mezzanine float.
  • the frame of the generators and hydraulics provides some longitudinal structural support to the float.
  • the hull structure will contain sealable ballast chambers so that desired mass properties can be obtained.
  • An example of a specific structural layout and overall shape is shown in Figure 14.
  • the heave plate will be manufactured from steel reinforced marine grade concrete.
  • this mass of the heave plate will be supported at three points around its circumference and so will be subject to bending loads.
  • pre-stressing the core steel frame can be done to improve the torsional and bending strength of the concrete structure. Tether interconnection points will be directly connected to the core steel reinforcement.
  • tethers will be constructed from large diameter synthetic lines, typically ultra-high molecular weight polyethelene or polyester. The choice of a particular tether material, in no way limits the scope of this invention. In some embodiments, the ends of these lines will be connected with a stainless steel interconnection. The choice of a particular material or type for this interconnection in no way limits the scope of this invention.
  • Figure 15 depicts an embodiment of a Load transfer unit 1500, shown in cutaway, with the primary hydraulic cylinder mounted at the one end and a simplified connection to the tether shown at the lower end.
  • load transfer units 1500 (LTU) (see e.g., Figure 15) that serve to linearize the loads from the tether and eliminate off-axis loadings to the primary hydraulic cylinder on the linear hydraulic gearbox.
  • LTU 1500 consists of a water lubricated tubular member that translates inside a steel tube that is structurally attached to the surface float core members.
  • the tubular translating member would have a steel core suitable for the tensions involved.
  • the core of the LTU 1500 would have a flange at one end that provides a mechanical limit to the motion (end- stop).
  • the core load bearing structure of the surface float would be designed around these three tether connection points and would aim to distribute this load evenly across the lower hull surface. These points are the key high stress locations on the surface float and will need to be reinforced accordingly.
  • each load transfer unit core would be directly attached to the piston of the primary hydraulic cylinder, which acts as the input to the hydraulic load transfer system.
  • the cylinder flange would be structurally mounted to transfer load effectively to the surface float core structure.
  • the secondary, output hydraulic cylinder would apply this load, conditioned by the hydraulic system, to the linear hydraulic generator, which would be mounted onto a mezzanine floor inside the hull structure of the surface float.
  • the secondary cylinder and stator would form a combined unit, which would react against each other and not transfer these loads to the surface float hull structure.
  • the heave plate in survival conditions, will be retracted and mated with the surface float, forming a single body 1600 (see e.g. , Figures 16 and 17). In such cases, structural loads will be significantly reduced and restricted to the hydrodynamic forces on the combined unit.
  • the flexible tethers in the system are an important element in regards to survival.
  • the simplicity of the system is such that the critical survival case occurs when the wave environment can potentially cause a slack event in one tether. This risk is highest when the device response is maximized.
  • a slack event where the load in the tether reduces to zero, an unpredictably large snap load will follow. This is mitigated by the ability to employ different system configurations depending upon the extremity of the sea state.
  • Some embodiments comprise an asymmetric heave plate that modifies the system dynamics to increase the minimum tether load and hence reduces the probability of slack loads:
  • a heave plate with flexible tethers When a heave plate with flexible tethers is employed, energy transfer is possible only when the float is moving up relative to the heave plate because of the need to maintain a positive tension in the tethers. As such, in some embodiments, it may be important that it returns to a mean position after each upward force is applied to the heave plate by the surface float.
  • the downward restoring force is provided by gravity alone and will be resisted by the hydrodynamic drag, inertia and damping of the heave plate.
  • Some embodiments of the system have a linear hydraulic gearbox that allows reconfiguration of the system stiffness and damping.
  • Some embodiments of this invention are methods for selecting system parameters that are appropriate for the sea state. For smaller wave conditions, such methods can increase displacement to achieve high efficiency. In larger wave conditions, such methods allow the stiffness of the system to be increased to change the frequency response of the system to reduce the motions and structural loadings.
  • some embodiments can employ a survival configuration. In these extreme sea states, the flexible tethers (or parallel lines) can be used to retract the heave plate so that it automatically mates with the surface float. In this configuration the device can now act like a single rigid body and becomes limited by the hydrodynamic forces on the single combined structure rather than the tether or reaction loads.
  • the entry into different device configurations will be triggered by the measured wave conditions at the site. At an individual device level, this would be a combination of the waves measured by an adjacent wave measurement buoy and the recorded motions and structural loads on the device itself.
  • a similar operating process will be used in array configurations, with the primary difference being that the information from multiple devices and measurement buoys can be used to provide more accurate information for decisions on how to control the array as a whole. This detailed information will be combined with wave forecasting to select the required system configuration.
  • Generators are modular and assembled remotely and shipped to site by standard road shipping. Structural steel is procured in bulk by the shipyard and typically transported via sea directly to the facility or by standard road shipping. Load -rated components may be assembled elsewhere and certified/proof tested before being shipped to the yard for integration into the hull. Hydraulics is shipped from vendor site directly to assembly dock by standard shipping. Power-electronics are shipped to assembly site from sub-system manufacturer first, prequalified at assembly site and shipped to dock for assembly. Winches for heave plate operations are shipped from vendor site directly to assembly dock by standard shipping.
  • the installation of the moorings is done with standard vessels.
  • the moorings are, in some embodiments, to be standard drag embedment anchors where the seabed allows; otherwise gravity or piled anchors will be used.
  • mooring lines are connected to locator floats at the planned location of the systems for easy retrieval during the system deployment, which may be a few days or even weeks later.
  • the deployment involves the mated system being towed to site using a standard tugboat with no specialized capability except the ability to carry a hydraulic compressor to power the deployment winches.
  • the mooring lines are disconnected from the locator buoys and connected by divers to the connection points on the surface float.
  • the locking clamps holding the heave plate and surface float together are then released, and the surface float is lowered using the on-board self-deploying strategy powered by the hydraulic pump carried by the tug.
  • the system described has inherently high reliability, the system architecture enables straightforward maintenance activities as needed.
  • the system has the ability for the heave plate to be recovered and mated to the surface float, whereby it can be disconnected from the moorings and towed to either a protected location or a port facility for work to be completed.
  • Planned maintenance can be completed on the device in- situ within reasonable weather windows.
  • the size of the device would allow internal access for service personnel, allowing safety and protection from the elements during operations.
  • the primary hydraulic driving cylinder circuit (connected to the LTU and directly loaded by the tether) can be locked, preventing any motion. This would then enable service operations to be completed on the drivetrain.
  • the heave plate can be raised slightly (or fully, depending upon operation) using the lifting lines that run parallel to the tethers. This would relieve the load on the tether and enable replacement of items in the load path.
  • the system may incorporate a structural health monitoring system that would monitor the condition of key components and advise of remaining lifetime and current health. This would be used to schedule maintenance on a just- in-time basis, ensuring minimum risk and minimum OPEX costs.
  • Types of on-board sensors/monitors include, but are not necessarily limited to, hydraulic pressure sensors, load cells, strain gauges, on-board CCD cameras with voice (for squeal detection), water level sensors, current sensors (corrosion protection system), oil quality sensors.
  • Planned maintenance Items that would be completed on set intervals are:
  • Components that are designed for a full lifetime, and would require only non- scheduled maintenance, triggered through problems detected in the health monitoring system are: Generator; Tether; Power Electronics; Hull Components.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Other Liquid Machine Or Engine Such As Wave Power Use (AREA)

Abstract

L'invention concerne un convertisseur d'énergie des vagues comprenant un flotteur de surface comprenant un profil non axisymétrique, une plaque de réaction configurée pour être immergée en dessous de la surface de l'eau, et plus d'une attache flexible, chacune étant mécaniquement accouplée à la fois au flotteur de surface et à la plaque de réaction, la plaque de réaction ayant un moment d'inertie dans le tangage et le roulis supérieur à un moment d'inertie dans le tangage et le roulis du flotteur de surface.
PCT/US2016/043721 2015-07-22 2016-07-22 Convertisseur d'énergie des vagues amélioré Ceased WO2017015626A1 (fr)

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US201562195693P 2015-07-22 2015-07-22
US62/195,693 2015-07-22
US15/217,772 2016-07-22
US15/217,772 US10393089B2 (en) 2013-04-05 2016-07-22 Wave energy converter

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GB202105936D0 (en) 2021-06-09
GB2594665A (en) 2021-11-03
GB2557501B (en) 2020-08-12
GB2594665B (en) 2022-03-02
GB202009919D0 (en) 2020-08-12
GB201802807D0 (en) 2018-04-04
GB202110860D0 (en) 2021-09-08
GB2584965A (en) 2020-12-23
GB2591421B (en) 2022-03-02

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