Dual-point absorber connected to a device

Abstract

To provide an improved device and method, capable of increasing power even outside a design period range, and capable of converting wave energy to electrical energy, the wave energy facilitating connection of some dual point absorbers to a facility on a water surface.SOLUTION: A dual point absorber comprises a first buoy, a second buoy and a power extraction device. The first buoy of the dual point absorber is connected to a link mechanism. The second buoy of the dual point absorber is movable with respect to the first buoy. The power extraction device is connected to the first buoy and the second buoy. The linkage mechanism can be used to reduce the vertical movement of the first buoy caused by waves.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention generally relates to a method and apparatus for converting wave energy into electrical energy. More particularly, the present invention relates to a dual point absorber connected to a platform.

Background Art

[0002] A dual point absorber is a type of wave energy converter (WEC) that generates power based on the relative displacement between its two floating bodies from waves in a body of water. In one such system, the two floating bodies are known as a float-and-spar absorber. Heretofore, the spar has been moored to the seabed using either a single-leg or a three-leg mooring system. Spar moorings, particularly those with three legs, can be expensive both in terms of components and installation / removal operations, and may have a large footprint on the seabed or a wide monitoring circle on the water surface, or both, and are difficult to assemble in a row. Further, when using the power generated by the float and spar absorber at a facility (e.g., a platform) on the water surface, an umbilical cable is required to extend downward from the spar to the seabed and then up through the water column to the facility on the water surface, which can be expensive.

[0003] Another possible problem is that the power generation response of the buoy and the spar absorber depends on the wave period, which means that the buoy and the spar absorber exhibit their highest performance in an intermediate range of periods, hereinafter referred to as the design period range or simply the design range. Outside of this range of periods, the response of the two floating bodies is generally small for short periods or synchronized for long periods. This means that the buoy and the spar absorber can only capture a small portion of the wave's hydrodynamic energy outside of the design range. In fact, the spar in the buoy and the spar absorber is not constrained against vertical movement, and thus a portion of the wave energy is stored in the spar in the form of kinetic energy and then dissipated in the form of viscous damping and drag without generating electricity.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] Accordingly, there continues to be a need in the art for methods and apparatus for converting wave energy into electrical energy, including a dual point absorber connectable to a surface facility. Preferably, these methods and apparatus increase the power generated, particularly outside of the design period range, in relation to a dual point absorber moored to the seabed. More preferably, these methods and apparatus facilitate the easy connection of multiple dual point absorbers to a surface facility.

MEANS FOR SOLVING THE PROBLEMS

[0005] The present disclosure describes a wave energy conversion device.

[0006] The wave energy conversion device can include a dual - point absorber that can include a first buoy, a second buoy, and a power extraction device. The first buoy can have a smaller hydrostatic stiffness against vertical movement compared to the second buoy. The first buoy can be heavier than the second buoy. The second buoy can be movable relative to the first buoy. The power extraction device can be coupled to the first buoy and the second buoy. The power extraction device can be configured to transmit the movement of the second buoy relative to the first buoy to a generator. In some embodiments, the dual - point absorber can not include an energy storage unit coupled to the generator.

[0007] The wave energy conversion device can include a link mechanism that can be connected to the first buoy of the dual - point absorber. The link mechanism can be further connected to a facility above the water surface. The link mechanism can be configured to reduce the vertical movement of the first buoy caused by waves during use. In some embodiments, the link mechanism can be movable relative to the facility above the water surface. For example, the link mechanism can include a first rod hinge - coupled to the first buoy and a second rod hinge - coupled to the first buoy. In some embodiments, the link mechanism can be configured to be fixed relative to the facility above the water surface.

[0008] In some embodiments, the wave energy conversion device can further include an energy storage system that can be attached to a facility above the water surface and an umbilical cable configured to connect to the generator and the energy storage system. The umbilical cable can also not be coupled to a seabed anchor.

[0009] In some embodiments, the wave energy conversion device can further include another power extraction device that can be coupled to the linkage mechanism. The other power extraction device can be coupled to the first rod of the linkage mechanism. In some embodiments, the wave energy conversion device can include a further power extraction device of a different type from the other power extraction device. The further power extraction device can be coupled to the second rod.

[0010] In some embodiments, the wave energy conversion device can further include a control device coupled to the other power extraction device. The control device can be programmed to monitor the sea state and decelerate or prevent the movement of the linkage mechanism based on the monitored sea state. The control device can receive a signal representing the movement of the first buoy, the movement of the second buoy relative to the first buoy, or the movement of the second buoy. Optionally, the control device can receive a signal representing the movement of the third buoy.

[0011] In some embodiments, the wave energy conversion device can include two shafts. Each of the two shafts can be coupled to one of the rods of the linkage mechanism at a connection point of the facility above the water surface. The input shaft of the differential gear can be coupled to (integrated with) the two shafts. The output shaft of the differential gear can be coupled to another generator.

[0012] In some embodiments, the wave energy conversion device can include two pumps. Each of the two pumps can be coupled to the linkage mechanism. The flows generated by the two hydraulic pumps can be combined to drive a single hydraulic motor. The single hydraulic motor can be coupled to another generator.

[0013] This disclosure describes a method of converting wave energy into electrical energy.

[0014] The method can include the step of providing a dual-point absorber that can include a first buoy, a second buoy, and a power take-off device. The first buoy of the dual-point absorber can be connected to a linkage mechanism. The second buoy of the dual-point absorber can be movable relative to the first buoy. The first buoy can have a smaller hydrostatic stiffness against vertical movement than the second buoy. The first buoy can be heavier than the second buoy. The power take-off device can be coupled to the first buoy and the second buoy. The power take-off device can be configured to transmit the movement of the second buoy relative to the first buoy to a generator.

[0015] The method can include the step of connecting the linkage mechanism to a facility above the water surface.

[0016] The method can include the step of reducing the vertical movement of the first buoy caused by waves via the linkage mechanism.

[0017] The method can include the step of generating electrical energy via a generator.

[0018] The method can include the step of providing an energy storage system on the facility above the water surface.

[0019] The method can include the step of connecting an umbilical cable to the generator and the energy storage system. The umbilical cable may not be coupled to a seabed anchor.

[0020] The method can include the step of providing another power take-off device. The another power take-off device can be coupled to the linkage mechanism.

[0021] The method can include the step of providing a control device. The control device can be coupled to the another power take-off device.

[0022] The method can include the step of using a control device to monitor the sea state.

[0023] The method can include the step of using a control device to decelerate or prevent the movement of the link mechanism based on the monitored sea state.

[0024] The method can comprise the step of providing two power take-off devices. Each of the two power take-off devices can be coupled to a link mechanism and another generator. The two power take-off devices can be coupled to the other generator such that each of the two power take-off devices applies torque to the other generator.

[0025] The method can include the step of generating electrical energy via the other generator.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 2A

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0027] The present disclosure describes a link mechanism for connecting a dual-point absorber to a facility on the water surface. The link mechanism is configured to reduce, minimize, and prevent the vertical movement of one of the buoys of the dual-point absorber. Although the drawings illustrate floats and spar absorbers, the present disclosure also contemplates other types of dual-point absorbers for converting wave energy into electrical energy.

[0028] FIG. 1 shows a facility 10 on the water surface and a dual-point absorber. The dual-point absorber includes two buoys floating on the sea surface 15, a spar 12 and a float 14, and a PTO called an internal PTO (i.e., inside the dual-point absorber formed only by the spar 12 and the float 14). The float 14 can move relative to the spar 12. The internal PTO is coupled to the spar 12 and the float 14 and is configured to transmit relative movement to a generator. Usually, the spar 12 has less hydrostatic stiffness against vertical movement but is heavier than the float 14. For example, the spar 12 can have a smaller waterplane area but a larger volume compared to the float 14. A link mechanism 16 connects the spar 12 to the facility 10 on the water surface. The link mechanism 16 is configured to reduce the vertical movement of the first buoy (i.e., the spar 12) caused by waves.

[0029] The spar 12 can be connected to the facility 10 on the water surface by a link mechanism 16 such as a four-bar link mechanism. As shown in FIG. 1, the spar 12 is a coupler of the four-bar link mechanism. Therefore, it is possible to limit the movement of the spar 12 to create a phase lag between the response of the float 14 and the response of the spar 12 to waves, and thus increase the amount of power generated under waves with periods outside the design period range. The movement limitation can be implemented in various ways, such as locking one or more of the joints or including elements that dampen rotation in one or more of the joints. Further, with the link mechanism 16, the system can maintain its nominal draft by adapting to tidal changes and high tides as needed.

[0030] In Figure 1, the crank and rocker of the four-bar link mechanism are illustrated as simple rods having ends coupled to the above-water facility 10 and the spar 12 via hinge joints. However, the crank and rocker can be implemented with other mechanical structures that can appropriately transfer the load applied on the spar 12 to the above-water facility 10. For example, the link mechanism 16 can include a structure similar to an open-end wrench that surrounds at least a part of the length of the spar 12 at one end. The structure can include a hinge joint that is movable relative to the above-water facility 10 at the other end. Alternatively, the link mechanism 16 can be fixed to the above-water facility 10.

[0031] The above-described four-bar link mechanism can be designed to be a parallelogram in order to keep the body of the spar 12 parallel to the above-water facility 10, which would be desirable in many applications.

[0032] Another means of restricting the movement of the spar 12 is achieved by simply locking one or more of the joints of the link mechanism 16 or by including external PTO(s) 18a, 18b in one (or more) of the joints, the crank, and the rocker. The PTOs 18a, 18b are called external PTOs because they are external to the dual-point absorber formed only by the spar 12 and the float 14. In these cases, additional electrical energy is generated from the waves, thereby increasing the efficiency of the system when capturing wave energy. Some embodiments of such concepts are illustrated in FIGS. 2, 2A, and 3. Preferably, the float and spar absorber and its internal PTO are designed for sea states where the waves are of short period and operate at least during this sea state. Further, the external PTO is preferably designed for sea states where the waves are of long period and operates at least during this sea state.

[0033] According to the sea state, i.e., wave height and wave period, either or both of the internal PTO and the external PTO can operate to generate electricity. For example, in order to monitor the sea state, a control device coupled to the internal PTO and / or the external PTO of the buoy and the spar absorber can be used. The control device can receive a signal representing the movement of the spar 12, a signal representing the movement of the buoy 14 relative to the spar 12, or both. In some embodiments, the signal representing the movement of the spar 12 and the signal representing the movement of the buoy 14 relative to the spar 12 can be combined or processed to generate a signal representing the movement of the buoy 14, which can then be received by the control device. Alternatively, the control device may receive a signal from an external buoy that moves with the waves. When the sea state is characterized by long-period waves, the control device can switch some of the electronics in the buoy and the spar absorber to sleep mode. Thus, electrical energy can be conserved when the buoy and the spar absorber do not generate as much electrical energy as needed. Further, when the sea state is characterized by short-period waves, the control device can prevent the movement of the link mechanism 16. For example, in addition to being coupled to the generator, the external PTOs 18a, 18b can be coupled to brakes. Thus, fast movements that would otherwise generate an excessive load on the external PTO and damage it are not transmitted to the external PTO, and the external PTO does not operate. There can be a sea state that belongs between a sea state characterized by short-period waves and a sea state characterized by long-period waves. In such a sea state, the electronics in the buoy and the spar absorber may not need to be switched to sleep mode, and the control device can only slow down the movement of the link mechanism 16.

[0034] In FIG. 2, the external PTO 18a is coupled to the shaft of the hinge joint of the crank and the rocker of the link mechanism 16. Less than two PTOs 18a can be implemented. In an alternative embodiment of the link mechanism 16, three or more PTOs 18a can be implemented.

[0035] In FIG. 2A, the external PTO 18a can each include a gearbox or a hydraulic pump and motor system, which are connected to a shaft extending from a crank and / or rocker forming a hinge joint. The gearbox or hydraulic pump and motor system enables conversion of the low-speed rotation of the shaft extending from the crank and / or rocker into high-speed rotation, which is then transmitted to the generator.

[0036] In an alternative case, the rotation of the crank of the link mechanism 16 and the rotation of the rocker of the link mechanism 16 can be transmitted to a differential gear having an output shaft coupled to a single generator. Thus, the torque applied to the generator by the output shaft is a combination of the torque applied to the differential gear by the crank and the torque applied to the differential gear by the rocker. Similarly, the flows generated by two hydraulic pumps can be combined to drive a single hydraulic motor coupled to the generator.

[0037] The hydraulic motor can include a vane motor, a gear motor, a geromotor, an axial piston motor, a radial piston motor, or another type of hydraulic motor. For example, the hydraulic motor can include a hydraulic jack that drives a screw of a ball screw system. The nut of the ball screw system can then be coupled to the generator.

[0038] In FIG. 3, the external PTO 18b can comprise components that can be arranged at one or more of the three illustrated positions. The two rod portions 19a and 19b can be extensions of each other or not, depending on whether any component of the external PTO 18b is arranged in an intermediate position. Further, the rod portions 19a and 19b can rotate, translate, or both, or not, with respect to the components of the external PTO 18b.

[0039] In some embodiments, the external PTO 18b can include a hydraulic piston and motor system connected to any rod of the link mechanism 16. The hydraulic piston and motor system enables conversion of the low-speed rotation of a shaft extending from the crank and / or rocker into high-speed rotation, which is in turn transmitted to the generator in this case as well. For example, the hydraulic piston can have a first end pinned to the crank of the link mechanism 16 and a second end pinned to the facility 10 above the water surface, and a flow is generated by a change in the distance between the first end and the second end. Alternatively, in other embodiments, the external PTO 18b can include a ball screw connected to any rod of the link mechanism 16. The ball screw enables conversion of the low-speed rotation of a shaft extending from the crank and / or rocker into high-speed rotation, which is in turn transmitted to the generator in this case as well. The nut of the ball screw can be directly pinned to a location on the crank of the link mechanism 16 or attached to a rod pinned to the crank of the link mechanism 16, and the screw can be pinned to the facility 10 above the water surface, whereby the screw rotates when the spar 12 moves within the wave.

[0040] Alternatively, the external PTO 18a and / or 18b can be formed by the shaft of a linear generator, or an extension of the shaft. The shaft or shaft extension can be hinged to the crank and / or rocker of the link mechanism 16. The stator of the electric linear generator can be hinged to the facility 10 above the water surface, whereby the wave generates a relative translational movement between the shaft of the generator and the stator of the generator. Conversely, the stator of the electric linear generator can be hinged to the crank and / or rocker of the link mechanism 16, and the shaft or shaft extension can be hinged to the facility 10 above the water surface.

[0041] The facility 10 on the water surface can be a fixed structure, for example, placed on the Earth (i.e., fixed to the seabed). Alternatively, the facility 10 on the water surface can be a large floating object such as a platform, because a large floating object acts like a fixed structure under long-span wave periods. However, unlike a fixed structure, a large floating object can move up and down with the tide and high tide. This difference can be advantageously used to simplify the design of the external PTO(s) 18a, 18b used with the buoy and the spar absorber connected to a large floating object, because the external PTO(s) 18a, 18b do not need to consider a range of motion as large as that in the case of a large floating object not connected to the buoy and the spar absorber.

[0042] The crank and the rocker have been illustrated as straight bars in FIGS. 1, 2, and 3 heretofore, but this is not essential. They can be formed according to strength and / or other design requirements, and they can have different outer shapes even if the four-bar linkage mechanism is not a parallelogram.

[0043] In some embodiments, an energy storage system is attached to the facility 10 on the water surface. An umbilical cable is connected to the internal PTO and the energy storage system. Thus, the energy storage system is not required inside the buoy and the spar absorber, whereby the buoy and the spar absorber can be made smaller. The umbilical cable is preferably not coupled to the seabed anchor.

[0044] It is possible to connect the linkage mechanism and an array of corresponding buoys and spar absorbers 20 to a platform 22 (e.g., a moored platform) as illustrated in FIG. 4. For example, the buoys and the spar absorbers 20 are arranged on one side of the platform 22, whereby the power generation capacity of a single buoy and spar absorber can be increased.

[0045] The present invention is capable of accepting various modifications and alternative forms, and specific embodiments thereof are shown by way of example in the drawings and description. However, it should be understood that the drawings and detailed description of the present invention are not intended to limit the claims to the particular forms disclosed, but on the contrary, are intended to cover all modifications, equivalents, and alternatives falling within the scope of the claims.

[0046] This application claims priority to U.S. Provisional Patent Application No. 63 / 000,269, filed Mar. 26, 2020, and U.S. Patent Application No. 17 / 200,173, filed Mar. 12, 2021.

Claims

1. A wave energy conversion device, A dual point absorber, including a first buoy, a second buoy and a power take-out device, wherein the second buoy is movable relative to the first buoy, and the power take-out device is coupled to the first buoy and the second buoy and configured to transmit the movement to a generator. A dual point absorber, A link mechanism connected to the first buoy of the dual point absorber, which is further connectable to a facility above the water surface and movable relative to the facility above the water surface. A link mechanism, Another power take-out device coupled to the link mechanism, Comprising, The link mechanism and the other power take-out device are configured to reduce the vertical movement of the first buoy caused by waves during use. A wave energy conversion device.

2. The first buoy has less hydrostatic rigidity and is heavier with respect to vertical movement than the second buoy. The wave energy conversion device according to Claim 1.

3. The dual point absorber does not include an energy storage unit coupled to the generator, and the wave energy conversion device, An energy storage system attachable to the facility above the water surface, An umbilical cable configured to connect to the generator and the energy storage system and not coupled to a seabed anchor. An umbilical cable, Further comprising the wave energy conversion device according to Claim 1.

4. A control device coupled to the other power take-out device, which monitors the sea state and is programmed to decelerate or prevent the movement of the link mechanism based on the monitored sea state. The wave energy conversion device according to Claim 1.

5. The control device receives a signal representing the movement of a third buoy. The wave energy conversion device according to Claim 4.

6. The control device receives a signal representing the movement of the first buoy, the movement of the second buoy relative to the first buoy, or the movement of the second buoy. The wave energy conversion device according to Claim 4.

7. The link mechanism includes a first rod hinged to the first buoy and a second rod hinged to the first buoy. The other power extraction device is coupled to the first rod. The wave energy conversion device includes a further power extraction device coupled to the second rod, and the further power extraction device is a different type of device from the other power extraction device. The wave energy conversion device according to claim 4.

8. Two shafts, each coupled to a rod of the link mechanism at a connection point of the link mechanism to the facility above the water surface, A differential gear having an input shaft coupled to the two rods and an output shaft coupled to another generator, The wave energy conversion device according to claim 1, further comprising.

9. Two pumps, each coupled to the link mechanism, A single hydraulic motor coupled to another generator, Further comprising, The flow generated by the two hydraulic pumps merges to drive the single hydraulic motor. The wave energy conversion device according to claim 1.

10. The link mechanism is configured to be fixed to the facility above the water surface. The wave energy conversion device according to claim 1.

11. A method of converting wave energy into electrical energy, Providing a dual point absorber, the dual point absorber including a first buoy, a second buoy and a power extraction device, the second buoy being movable relative to the first buoy, the power extraction device being coupled to the first buoy and the second buoy and configured to transmit the movement to a generator, the first buoy of the dual point absorber being connected to a link mechanism, Providing another power extraction device coupled to the link mechanism, Connecting the link mechanism to a facility above the water surface, Reducing the vertical movement of the first buoy caused by waves through the link mechanism by using the other power extraction device, Generating electrical energy through the generator, Including, method.

12. The first buoy is less hydrostatically rigid and heavier for vertical movement than the second buoy. The method according to claim 11.

13. Providing an energy storage system on the facility above the water surface, Connect an umbilical cable to the generator and the energy storage system, and the umbilical cable is not coupled to a subsea anchor, The method according to claim 11, further comprising.

14. Provide a control device, the control device being coupled to the other power take-off device, Use the control device to monitor the sea surface conditions, Use the control device to decelerate or prevent the movement of the link mechanism based on the monitored sea surface conditions, The method according to claim 11, further comprising.

15. Providing two power take-off devices, each of the two power take-off devices being coupled to the link mechanism and another generator, Couple the two power take-off devices to the other generator, whereby each of the two power take-off devices applies torque to the other generator, Generating electrical energy via the other generator, The method according to claim 11, further comprising.

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