Wave Energy Converter

Abstract

A wave energy converter is provided, including a nacelle having starboard and port side axes and housing a power take-off device. The wave energy converter also includes a buoyant member coupled to the nacelle and a ballast tank coupled to the nacelle. The ballast tank, buoyant member, and nacelle together form a first body, and the first body is coupled to the power take-off device. The wave energy converter further includes a float and a drive arm forming a second body, the second body being rotatably coupled to the first body about a coupling axis, and the second body being coupled to the power take-off device. The second body is configured to rotate relative to the first body about the coupling axis within a radial span bounded by a proximal end of the float and a radially distal end of the float. According to one aspect, the first body has a center of mass and a center of buoyancy, and the coupling axis is offset from a line formed between the center of mass and the center of buoyancy of the first body. A method of generating electricity using a wave energy converter is also provided.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to converting wave surge and heave into energy, and more particularly to wave energy conversion devices and methods. [Background technology]

[0002] Ocean energy, particularly wave energy, is a consistent, reliable, and predictable energy resource that is widely available and close to many population centers. Most of the world's population lives within 200 miles (322 km) of the ocean, making it an accessible renewable energy source. Environmentally, waves are one of the most benign clean renewable energy sources. This set of characteristics makes wave energy unique among the most widely available global renewable energy resources.

[0003] Wave energy is a globally desirable resource and has the potential to be a cost-competitive and important component in a diverse mix of clean renewable energy resources.

[0004] What is needed is a wave energy conversion device that efficiently and cost-effectively converts ocean wave energy into rotational motion for direct drive rotary power generation while achieving improved reliability and survivability. Summary of the Invention [Means for solving the problem]

[0005] According to one aspect, there is provided a wave energy converter including a nacelle having a starboard side and a port side and housing a power take-off device. The wave energy converter also includes at least one buoyant member coupled to the nacelle, and a ballast tank coupled to the nacelle such that the buoyant member, the ballast tank, and the nacelle together form a first body, the first body being coupled to the power take-off device. The wave energy converter further includes a float and a drive arm forming a second body, the second body being rotatably coupled to the first body about a coupling axis, and the second body being coupled to the power take-off device. The second body is configured to rotate relative to the first body about the coupling axis within a radial span bounded by a proximal end of the float and a radially distal end of the float.

[0006] According to another aspect, there is provided a wave energy converter including a nacelle having a starboard side and a port side and housing a power take-off device. The wave energy converter also includes at least one buoyant member coupled to the nacelle, and a ballast tank coupled to the nacelle such that the buoyant member, the ballast tank, and the nacelle together form a first body, the first body being coupled to the power take-off device. The wave energy converter further includes a float and a drive arm forming a second body, the second body being rotatably coupled to the first body about a coupling axis, and the second body being coupled to the power take-off device. The second body is configured to rotate relative to the first body about the coupling axis within a radial span bounded by the proximal end of the float and the radially distal end of the float. The first body also has a center of mass and a center of buoyancy, the coupling axis being offset from a line formed between the center of mass and the center of buoyancy of the first body.

[0007] According to yet another aspect, a method of generating electricity is provided. The method includes the step of: a) providing a wave energy converter including a nacelle having a starboard side and a port side and housing a power take-off device. The wave energy converter also includes at least one buoyant member coupled to the nacelle, and a ballast tank coupled to the nacelle such that the buoyant member, the ballast tank, and the nacelle together form a first body, the first body being coupled to the power take-off device. The wave energy converter further includes a float and a drive arm forming a second body, the second body being rotatably coupled to the first body about a coupling axis, and the second body being coupled to the power take-off device. The second body is configured to rotate relative to the first body about the coupling axis within a radial span bounded by a proximal end of the float and a radially distal end of the float. The method also includes the step of: b) operating the wave energy converter in a wave field. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view of a wave energy converting device according to an embodiment; FIG. [Figure 2] FIG. 2 is a front view of the wave energy converting device shown in FIG. 1. [Figure 3] FIG. 2 is a top view of the wave energy converting device shown in FIG. 1; [Figure 4] FIG. 2 is a side view of the wave energy converting device shown in FIG. 1; [Figure 5] Figure 10 shows a detailed view of the buoyancy member and spar joint in a wave energy converter according to an embodiment; [Figure 6] 1 is a cross-sectional top view of a wave energy converting device according to an embodiment; [Figure 7] FIG. 2 is a detailed cross-sectional front view of a portion of a nacelle and nacelle tube according to one embodiment. [Figure 8] 1 is a schematic side view of a wave energy converting device according to an embodiment; [Figure 9] 1 is a schematic side view of a conventional wave energy conversion device; [Figure 10]1 is a schematic side view of a wave energy converting device according to an embodiment; [Figure 11] Figure 2 is a schematic top view of a wave energy converting device according to another embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0009] The technology of this disclosure relates to a wave energy converter (WEC) useful for converting energy associated with offshore wave heave and surge into rotational power. This disclosure builds on technology disclosed in Applicant's prior patents related to WECs, including U.S. Patent No. 9,587,620, filed September 30, 2013; U.S. Patent No. 8,508,063, filed October 22, 2012; U.S. Patent No. 8,314,506, filed February 22, 2010; and U.S. Patent No. 8,659,179, filed August 12, 2013, all of which are incorporated herein by reference in their entireties. These prior patents disclose wave energy converter technology and describe in detail some of the internal components of WECs.

[0010] In general overview, wave energy converters (WECs) can be used in a variety of autonomous and grid-connected applications, including, but not limited to, low-power sensors, marine vessels and ships, desalination, aquaculture, offshore oil and gas platforms, and utility-scale grid connections. WECs are floating multibody systems with nacelles buoyantly supportable above the water surface that convert the heave and surge of offshore waves into rotational torque that can drive direct-drive generators or pumps.

[0011] The ultimate goal of a wave energy converter (WEC) is to convert one form of energy into another, in this case a chain involving hydrodynamic conversion into power and ultimately into electricity or other easily transportable forms. Due to the nature of the energy source, WECs pose a unique set of design requirements: very low speeds, very high forces, and cyclical, abrupt, and chaotic operation.

[0012] In the wind industry, large diameter direct drive generators have proven to be a viable technical approach at low speeds, and WECs can be similarly viable by addressing the challenges posed by extracting power at very low speeds. Thus, as described in Applicant's prior patents, various embodiments may utilize direct drive, thereby eliminating the need for a gearbox, improving reliability, and reducing the need for expensive vessel maintenance.

[0013] As described in more detail below, aspects of the present disclosure relate to a WEC having improved performance characteristics compared to conventional WEC configurations. Broadly speaking, a WEC can include a first body and a second body. Relative motion between the two bodies generates power at a power take-off device.

[0014] As will be described in more detail below, portions of the WEC can function as hydrostatic springs to improve energy capture. As a brief overview, a WEC can be designed so that the first body tends to pitch about its center of mass. This is shown in Figure 8 and will be described in more detail below. However, first, the general components of a WEC will be described.

[0015] A WEC and / or particular components of the WEC may be described as having a fore-side, an aft-side, a starboard side, and a port side, as these terms are common to those skilled in the art. Those skilled in the art will recognize that these conventional terms are intended to refer to one side relative to another (i.e., the fore-side is opposite the aft-side, the starboard side is opposite the port side, the port side is the left side when looking forward, and the starboard side is the right side when looking forward). These terms may also be used to describe a desired orientation for optimal energy capture. However, it should also be understood that these terms are not intended to be limiting, as the WEC may move and / or rotate when operating in an underwater wave field.

[0016] 1-6 , one embodiment of a wave energy converter (WEC) 100 includes a buoyant nacelle 102. As described in more detail below, the nacelle 102 houses a power take-off device. The WEC further includes at least one buoyant member 60, 70 coupled to the nacelle 102. Also coupled to the nacelle 102, as shown, is a ballast tank 50. As described in more detail below, the ballast tank 50 serves as the primary mass element for a first body, which may be filled with a material such as, but not limited to, water, sand, concrete, and / or PERMA BALLAST®, to submerge the ballast tank 50 to its operational state. The ballast tank 50, the at least one buoyant member 60, 70, and the nacelle 102 together form a first body that is coupled to a power take-off device housed within the nacelle 102.

[0017] As shown in FIGS. 1-4 , the WEC 100 also includes a float 108 and a drive arm 110 that form a second body, the second body being rotatably coupled to the first body about a connecting shaft 20. The second body is also coupled to a power take-off device, and the second body is configured to rotate relative to the first body about the connecting shaft 20 within a radial span encompassed by a proximal end 202 of the float 108 and a radially distal end 204 of the float 108. As shown in FIGS. 1-4 , in one embodiment, the nacelle 102 has a longitudinal axis, and the connecting shaft 20 is aligned with the longitudinal axis. However, it is contemplated that in other embodiments, the connecting shaft 20 may be offset from the longitudinal axis of the nacelle 102.

[0018] In one embodiment, the float 108 is configured to move a full 360° around the nacelle 102. It should be appreciated that in another embodiment, the float 108 may be configured to move less than 360°. For example, there may be a mechanical stop to limit the rotation of the float 108. In another embodiment, described in more detail below, the float 108 may be configured to move less than 360° in a configuration in which the float arms are external to the buoyant member 60. As described in more detail below, the second body is operably coupled to a power take-off device via the drive arm 110. As described in more detail below with reference to the embodiment shown in FIG. 7, the float 108 is operably coupled to a power take-off device mounted inside the nacelle 102.

[0019] In one exemplary embodiment, the at least one buoyant member 60, 70 includes a first buoyant member 60 and a second buoyant member 70. However, it should be understood that the present disclosure is not limited thereto and contemplates embodiments having only one buoyant member and / or three or more buoyant members. Also, as shown in Figures 1-4, in one embodiment, the first buoyant member 60 is coupled to the starboard side of the nacelle 102 and the second buoyant member 70 is coupled to the port side of the nacelle 102.

[0020] In one particular embodiment, the first buoyant member 60 is configured as a pontoon and the second buoyant member 70 is also configured as a pontoon. In one embodiment, the first and second buoyant members 60, 70 each have a substantially hollow cylindrical body. Those skilled in the art will recognize that in other embodiments, at least one buoyant member may be shaped and / or configured differently, such as, but not limited to, a U-shaped buoyant member, a rectangular parallelepiped connecting pontoons, a shape having a raindrop cross section, and / or an irregularly shaped buoyant member.

[0021] 1-4 , the WEC 100 further includes a nacelle tube 80 having a first end extending outwardly from the starboard side of the nacelle 102 and a second end extending outwardly from the port side of the nacelle 102. As shown, a first buoyant member 60 is coupled to the starboard side of the nacelle tube 80, and a second buoyant member 70 is coupled to the port side of the nacelle tube 80. In this particular embodiment, a ballast tank 50 is coupled to both the first and second buoyant members 60, 70. As shown, the ballast tank 50 extends substantially below the nacelle 102. A first spar 104 may extend downwardly from the first buoyant member 60 to connect the first buoyant member 60 to the ballast tank 50, and similarly, a second spar 106 (see FIG. 2) may extend downwardly from the second buoyant member 70 to connect the second buoyant member 70 to the ballast tank 50.

[0022] As described in more detail below, in one particular embodiment, the WEC has a first body including multiple buoyant members 60, 70, each coupled to one end of a ballast tank 50 in a triangular spar configuration (with spars 104, 106 and knee braces 30, 32, as shown in FIG. 4). In one embodiment, the WEC has a second body including a single float that rotates relative to the first body. As described in more detail below, the first body can be configured to provide a large restoring force.

[0023] While nacelle tubes 80 are shown in Figures 1-4, the present disclosure also contemplates embodiments that do not have nacelle tubes 80 or that are configured differently. For example, in one embodiment, nacelle tubes 80 may be internal to the nacelle such that there are no nacelle tubes extending outward from the nacelle to the buoyancy member. One exemplary embodiment is shown in Figure 11 and described in more detail below.

[0024] As shown in FIGS. 1-6 , the first body components (buoyancy members 60, 70, nacelle 102, and ballast tank 50), and in this exemplary embodiment, the nacelle tube 80 and spars 104, 106, are rigidly joined to one another. FIG. 5 is a detailed view of one embodiment of such a rigid joint, which is a welded buoyancy member-spar joint. As shown in FIG. 5 , the nacelle tube 80, first buoyancy member 60, and first spar 104 may be welded to one another at a first joint on the starboard side of the WEC 100. Similarly, the nacelle tube 80, second buoyancy member 70, and second spar 106 may be welded to one another at a second joint located on the port side of the WEC 100. Similar weld joints may secure the lower portions of the first and second spars 104, 106 to each end of the ballast tank 50. Although a welded joint is shown, the present disclosure contemplates other rigid joints, including, but not limited to, integrally formed parts that can be molded or 3D printed, mechanical fasteners such as, but not limited to, bolts and clamps, and in one embodiment, adhesives can be used.

[0025] Also as shown in Figure 1, in one exemplary embodiment, a first end of the nacelle tube 80 is coupled to the forward end (i.e., front) of the first buoyant member 60. Similarly, as shown in Figure 1, a second end of the nacelle tube 80 may be coupled to the forward end of the second buoyant member 70. In one embodiment, the nacelle tube 80 is coupled to the first and second buoyant members 60, 70 at their forward ends. As described in more detail below, this configuration allows the WEC to function as a hydrostatic spring, improving the energy capture of the WEC.

[0026] 1-4, in one embodiment, the first and second buoyant members 60, 70 both have an elongated shape. As shown, a first end of a nacelle tube 80 can be coupled to one end of the elongated first buoyant member 60, and a second end of the nacelle tube 80 can be coupled to one end of the elongated second buoyant member 70.

[0027] In one embodiment, the first and second buoyant members 60, 70, the nacelle 102, the nacelle tube 80, the ballast tank 50, and the float 108 each have a hollow, substantially cylindrical body. It is believed that a cylindrical shape can optimize material strength and reduce manufacturing costs due to ease of manufacture. Other shapes are also contemplated for one or more of these components, including, but not limited to, rectangular, spherical, and irregularly shaped bodies.

[0028] 1 and 4, in one exemplary embodiment, the WEC 100 further includes a first knee brace support 30 extending downward from the first buoyant member 60 to the ballast tank 50, and a second knee brace support 32 extending downward from the second buoyant member 70 to the ballast tank 50. It should be appreciated that the first and second knee brace supports 30, 32 are configured to provide additional support to the first body. As shown in the figures, in one exemplary embodiment, the first knee brace support 30 extends downward from the aft (i.e., rear) side of the first buoyant member 60, while the first spar 104 extends downward from the forward end of the first buoyant member 60, such that the first buoyant member 60, the first spar 104, and the first knee brace support 30 collectively form a triangular shape. Similarly, in one exemplary embodiment, the second knee brace support 32 extends downwardly from the aft side of the second buoyant member 70, while the second spar 106 extends downwardly from the forward end of the second buoyant member 70, such that the second buoyant member 70, the second spar 106, and the second knee brace support 32 collectively form a triangular shape on the other side of the WEC 100. It should be appreciated that the first and second knee brace supports 30, 32 may be welded or otherwise rigidly connected to the ballast tank 50 and their corresponding first and second buoyant members 60, 70.

[0029] As shown, in one embodiment, the first and second spars 104, 106 and / or the first and second knee braces 30, 32 each have a hollow, substantially cylindrical body. As discussed above, it is believed that a cylindrical shape can optimize material strength and reduce manufacturing costs due to ease of manufacture. Other shapes are also contemplated for one or more of these components, including, but not limited to, rectangular, spherical, and irregularly shaped bodies.

[0030] Also, in one embodiment, the first and second spars 104, 106 and / or the first and second knee braces 30, 32 may be buoyant components. However, in other components, the first and second spars 104, 106 and / or the first and second knee braces 30, 32 (i.e., the connections between the ballast tanks 50 and the nacelle 102, nacelle tubes 80, and / or buoyant members 60, 70) may not be buoyant. It is contemplated that the knee braces 30, 32 and / or spars 104, 106 may be rigid or non-rigid. For example, in one embodiment, the first and second spars 104, 106 and / or the first and second knee braces 30, 32 may include rigid components such as beams, trusses, steel plates, and / or rods, although the disclosure is not so limited. In one embodiment, non-rigid connections are contemplated; for example, the first and second spars 104, 106 and / or the first and second knee braces 30, 32 may be made of chains, cables, straps, and / or ropes.

[0031] As noted above, the present disclosure relates to a WEC design with improved performance characteristics. As noted above, portions of the WEC can function as hydrostatic springs to enhance energy capture. The inventors recognized that varying the relationship between the center of mass and the center of buoyancy can induce instability in the WEC, optimizing the WEC's resonant response and increasing energy capture. In one embodiment, the first and second buoyant members 60, 70 function as the primary buoyancy elements of the first body, and the ballast tank 50 functions as the primary mass element of the first body. As shown in the schematic side view of FIG. 8, the first body tends to pitch about its center of mass (which is kept low by the ballast tank 50), so the buoyant members 60, 70 function as hydrostatic springs and can exert a large restoring torque. The vertical separation of the center of buoyancy and the center of mass, along with the orientation of the waterline areas of the buoyant members, enhances the restoring force when the WEC 100 pitches. This contrasts with the schematic side view of a conventional WEC shown in FIG. 9. As shown in Figure 9, the center of buoyancy of the first body does not move substantially as the body rotates in water, so the restoring force is minimal.

[0032] According to aspects of the present disclosure, the second body, including the float 108 and drive arm 110, can be optimized to have a response that is out of phase and / or amplitude with the first body to maximize relative motion for energy capture. FIG. 10 builds from the schematic side view shown in FIG. 8 and further illustrates the connection shaft 20 between the first body (including at least one buoyant member 60, ballast tank 50, and nacelle 102) and the second body (the float 108 and drive arm 110). As shown, in one embodiment, the nacelle has a longitudinal axis, and the connection shaft 20 is aligned with the longitudinal axis of the nacelle 102. As shown in FIG. 10, pitching motion of the first body results in a heaving (up and down) motion at the ends of the buoyant members 60, 70. As the first body pitches forward (as indicated by the clockwise arrow in FIG. 10), the relatively high mass of the first body pushes the connection point down into the water (as indicated by the vertical arrow below the connection shaft 20). The relatively light and buoyant second body (float 108 and drive arm 110) cannot be easily pushed into the water, so when the attachment point is pushed down and the sea surface restrains the second body, it is forced to pitch upward (as shown by the counterclockwise arrow in Figure 10). Thus, clockwise motion of the first body results in simultaneous counterclockwise motion of the second body, which is ideal for energy capture.

[0033] In other words, in one exemplary embodiment, the first body has a center of mass and a center of buoyancy, as shown in Figure 10. As shown, the connecting axis 20 is offset from a line formed between the center of mass and the center of buoyancy of the first body. As shown, the longitudinal axis of the nacelle 102 is also the connecting axis 20, and this axis is about which the second body (float 108 and drive arm 110) rotates relative to the first body to generate energy in the WEC 100.

[0034] In one embodiment, the nacelle 102 can be described as a substantially watertight housing within which one or more rotary power take-off devices can be housed. In another embodiment, the nacelle 102 need not be substantially watertight, provided that the internal components are configured to withstand the marine environment and maintain buoyancy. In one embodiment, the nacelle 102 can include an empty buoyant shell that can house power generation, maintenance, and / or other equipment, or can be used for any other suitable purpose. It should be appreciated that the nacelle outer shell (i.e., the nacelle hull), along with the buoyancy members 60, 70 and ballast tanks 50, can be part of the first body described above. In one embodiment described below, the nacelle 102 includes one power take-off device. As described below, the present disclosure also contemplates embodiments having two or more power take-off devices. As described in more detail below, energy can be generated in the power take-off devices as long as there is relative motion between the first body and the second body.

[0035] As mentioned above, in one embodiment, the first body (i.e., the nacelle 102, at least one buoyant member 60, 70, and ballast tank 50) and the second body (i.e., the float 108 and the drive arm 110) are operably connected to one or more power take-off units (PTOs) mounted within the nacelle 102. In another embodiment, the nacelle 102 and the PTOs may be incorporated into the at least one buoyant member 60, 70. As shown in FIG. 1 , in one embodiment, the first body also includes a nacelle tube 80 having a first end extending outwardly from the starboard side (i.e., right side) of the nacelle 102 and a second end extending outwardly from the port side (i.e., left side) of the nacelle 102. 1, the float arms 110 may include a first float arm 110 rotatably coupled to the starboard side of the nacelle tube 80 and a second float arm 110' rotatably coupled to the port side of the nacelle tube 80. It should be appreciated that in one embodiment, one float arm 110 may function as a drive arm and the other float arm 110' may function as an idler arm.

[0036] 7 shows a partial cross-sectional view of the nacelle 102 and the nacelle tube 80. As mentioned above, in one embodiment, the float 108 includes two spaced apart float arms 110, 110', one functioning as a drive arm and the other functioning as an idler arm. In one embodiment, the drive arm is coupled to the nacelle tube 80 on one side of the nacelle 102, and the idler arm is coupled to the other side of the nacelle tube 80. FIG. 7 shows one side of the nacelle tube 80. Of course, the other side of the nacelle tube 80 may include similar components.

[0037] As shown in FIG. 7 , one of the float arms 110, 110′ can function as a drive arm and can be operably coupled to a drive shaft 251 disposed inside the nacelle 102. In an exemplary embodiment, a torque tube 112 extends outward from each side of the nacelle 102. The float arms 110, 110′ can be coupled to the torque tube 112 such that movement of the float arm 110, 110′ causes movement of the torque tube 112, which in turn causes movement of the drive shaft 251. As shown in FIG. 7 , in one embodiment, the torque tube 112 can include a plurality of ribs 114 on both ends, which can be used to secure the float arms 110, 110′ to the torque tube 112. As also shown in FIG. 7 , bearings 265 can be provided to allow rotation of the float arms 110 and torque tube 112 relative to the inner nacelle tube 80. As described in more detail in Applicant's prior patents referenced above, movement of float arm 110 in turn moves drive shaft 251, which in turn generates power or electricity in at least one power take-off device within the nacelle. As described in more detail below, in one particular embodiment, the power take-off device includes rotor components (220, 255) and stator components (210, 270) shown in Figure 7. In one embodiment, relative motion between the second body and the first body generates energy in the power take-off device.

[0038] Details regarding specific PTO configurations can be found in Applicant's prior patents related to WECs, such as U.S. Patent No. 9,587,620, filed September 30, 2013; U.S. Patent No. 8,508,063, filed October 22, 2012; U.S. Patent No. 8,314,506, filed February 22, 2010; and U.S. Patent No. 8,659,179, filed August 12, 2013. In summary, those skilled in the art will appreciate that such PTOs, in some embodiments, can comprise one or more direct-drive generators, gearbox-driven generators, hydraulic systems, pumping systems, water pumps, water pumps, water desalination systems, air pumps, hydraulic pumps, etc. In various pump and hydraulic-related embodiments, the drive shaft / hub can be directly or indirectly connected to, for example, an impeller, a compressor rotor, and / or a mechanical turbine rotor. In some power generation embodiments, the drive shaft / hub can be directly or indirectly connected to, for example, one or more rotors and / or stators. However, in view of this disclosure, it will be understood that there are many other design alternatives for the PTO components mounted within the nacelle than those described above, and these alternatives are within the scope of this disclosure.

[0039] 7, those skilled in the art will appreciate that in power generation applications, a rotary PTO can include one or more rotor segments 220 rotatable relative to one or more stator segments 210. As described in more detail in applicant's prior patents referenced above, relative rotation between rotor segments 220 and stator segments 210 can be achieved by drive bearings 261, 262, or any other bearing or similar mechanism that allows one or more components to rotate freely around or within another component. The rotor can be operably connected to any drive shaft / hub via any suitable means.

[0040] 7, the drive shaft 251 may generally rotate about the connecting shaft 20 on a drive bearing or other suitable structure. In various embodiments, the drive shaft 251 may be sealed by one or more seals 280 to prevent ingress of seawater and / or harmful foreign objects / debris. In one embodiment, the power take-off is a direct drive generator having a rotor assembly and a stator assembly, the rotor assembly rotating about the connecting shaft 20. In one embodiment, the second body (the float 108 and the float arms 110, 110′) is operably coupled to the rotor assembly of the power take-off, and the first body (the first and second buoyant members 60, 70, the nacelle tube 80, and the ballast tank 50) is fixed to the stator assembly of the power take-off.

[0041] In one embodiment, the rotary PTO may be a direct drive system (e.g., a low-speed, high-torque system). Such systems have proven to be a viable technological approach in connection with wind energy utilization, and similar low-speed principles apply to marine situations. However, the techniques described herein may be implemented using any type of rotary PTO, including, but not limited to, a generator, a gearbox and generator, a hydraulic system and generator, a water pump, and / or any other suitable rotary PTO device.

[0042] 7 provides a partial cross-sectional top view of the nacelle 102 and nacelle tube 80. In the embodiment shown in FIG. 7, a rotary PTO is provided. In power generation applications, such a rotary PTO may include one or more rotor segments 220 that are rotatable relative to one or more stator segments 210. Depending on the application, the stator segments 210 may be independently rotatable relative to the nacelle 102 or may be held in a fixed rotational position. As described in more detail below, relative rotation between the rotor segments 220 and the stator segments 210 may be achieved by drive bearings or any other bearing or similar mechanism that allows one or more components to freely rotate around or within another component.

[0043] In one embodiment, one or more rotor segments 220 may be directly integrated with the drive shaft 251 and rotor hub / tire 255. As shown in FIG. 7 and described above, the drive shaft / hub may be connected to a torque tube 112 that is connected to one or more rotors. However, in view of the present disclosure, it will be apparent that the rotors may be operably connected to any drive shaft 251 / hub 255 by any other suitable means, including, but not limited to, a gearbox or transmission, bolting, etc. Additionally, one or more stator segments 210 may be fixedly or rotatably attached to the nacelle 102, as described in Applicant's prior patents.

[0044] 7 shows the WEC 100 with one PTO, it will be apparent in view of this disclosure that any number of PTOs may be used. For example, in one embodiment, there may be two drive arms 110 coupled to the float 108, with both the first and second drive arms rotatably coupling the float 108 to the nacelle tube 80. In this embodiment, the second body (float 108 and associated drive arms) is operably coupled to a power take-off device via both the first and second drive arms 110.

[0045] In another embodiment, the power take-off device includes a first power take-off device and a second power take-off device. In this embodiment, the second body can be operably connected to the first power take-off device via a first drive arm, and the second body can be operably connected to the second power take-off device via a second drive arm. In one embodiment, the first and second power take-off devices are each direct drive generators having a rotor assembly and a stator assembly. The rotor assemblies of the first and second power take-off devices can rotate about a connecting shaft 20.

[0046] In yet another embodiment, the power take-off devices include a first plurality of power take-off devices and a second plurality of power take-off devices. The second body can be operably coupled to the first plurality of power take-off devices via a first drive arm, and the second body can be operably coupled to the second plurality of power take-off devices via a second drive arm. It is also contemplated that in one embodiment, multiple drive shafts can be provided, with each drive shaft capable of driving one or more PTOs. Those skilled in the art will appreciate that multiple PTOs can be provided within the nacelle 102 with the addition of mechanical components such as gears.

[0047] The nacelle 102, buoyancy members 60, 70, ballast tank 50, and spars 104, 106 may be fabricated from composite materials (e.g., carbon fiber, Kevlar, fiberglass, etc.), concrete, rolled steel, aluminum, and / or any other suitable metal or alloy. In some embodiments, the nacelle 102 and / or buoyancy members 60, 70 may include an access hatch 128 for loading / unloading equipment and personnel (e.g., for maintenance and repair). In one embodiment, at least one of the nacelle 102, nacelle tube 80, first and second buoyancy members 60, 70, first and second spars 104, 106, and ballast tank 50 includes one or more waterproof modules. In one embodiment, each of the above components is fabricated from a waterproof module.

[0048] As described above, the first spar 104 and the second spar 106 connect the first and second buoyancy members 60, 70 to the ballast tank 50. A spar (e.g., 104, 106), as that term is used herein, comprises a hollow or solid elongated element. The cross-sectional shape of each spar 104, 106 may be any suitable shape (e.g., circular, triangular, airfoil-shaped, elliptical, etc.). The spars 104, 106 may be fabricated from composite materials (e.g., carbon fiber, Kevlar®, fiberglass, etc.), concrete, rolled steel, aluminum, and / or any other suitable metal or alloy. Depending on the scale, one or more of the spars 104, 106 may be hollow, compartmentalized, or modularized to accommodate or provide access to ballast, equipment, and personnel associated with power generation, maintenance, ballasting, etc. The spars 104, 106 may generally be attached directly or indirectly to opposite ends of the ballast tank 50. In some embodiments, the first spar 104 is welded at one end to the first buoyancy member 60 on the starboard side of the nacelle tube 80 and the second spar 106 is welded at one end to the second buoyancy member 70 on the port side of the nacelle tube 80, although it will be apparent in view of this disclosure that other suitable attachment methods may be used.

[0049] As shown in FIGS. 4 and 6 , in some embodiments, one or more upper spars 124, 126 may extend upward from the first and second buoyant members 60, 70 to serve as mooring posts or attachment structures (e.g., antennas, solar panels, warning lights, etc.). As shown, various embodiments may include a boarding area 34 (e.g., a service platform and / or docking equipment) attached to one or more spars 124, 126 and / or buoyant members 60, 70 to improve servicing access for an activated WEC 100. A spar access hatch 128 may be provided on the upper spars 124, 126 and / or buoyant members 60, 70. The spar access hatch 128 is generally above the waterline in non-storm conditions and is designed to allow maintenance personnel and / or equipment to enter and exit the WEC 100 to further access its components and internal equipment.

[0050] FIG. 11 is a schematic top view of a wave energy converter according to another embodiment. This embodiment includes some of the components described above, and therefore, some components have the same reference numerals. However, unlike some of the above-described embodiments, this particular embodiment does not have a nacelle tube connecting the nacelle 102 to the rest of the body. As shown, in this exemplary embodiment, the WEC 200 includes three-piece nacelles 102a, 102b, and 102c, with one of the nacelle components 102a, 102b, and 102c housing a power take-off device. The WEC 200 also includes at least one buoyant member 60 coupled to the nacelles 102a, 102b, and 102c. A ballast tank (not shown) may be provided such that the ballast tank, the nacelles 102a, 102b, and 102c, and the at least one buoyant member 60 form a first body coupled to the power take-off device. The float 108 and the drive arm 110 form a second body that is rotatably coupled to the first body about a connecting shaft 20, and the second body is also coupled to the power take-off device. The second body is configured to rotate relative to the first body about the connecting shaft 20 within a radial span bounded by a proximal end 202 of the float 108 and a radially distal end 204 of the float 108.

[0051] In this embodiment, the float 108 can include a float arm 110 that can function as a drive arm, and another float arm 110' that can function as an idler arm. The float / drive arm 110 can be located inside the nacelle outer wall, and the drive arm 110 can be rotatably coupled about a coupling axis to the first body at a location between the two portions of the nacelles 102a, 102b. Similarly, the float idler arm 110' can be located inside the nacelle outer wall, and the idler arm 110' can be rotatably coupled about a coupling axis to the first body at a location between the two portions of the nacelles 102b, 102c. In one embodiment, there can be one buoyancy member 60 that extends across both the starboard and port sides of the nacelles 102a, 102b, 102c. In another embodiment, there can be a first buoyancy member 60 on the starboard side of the nacelle and a second buoyancy member 70 on the port side of the nacelle. As mentioned above, in one embodiment, the buoyant members 60 may be configured as pontoons. In another embodiment, at least one buoyant member may be configured as a spar. Figure 11 shows an embodiment in which the float / drive arms 110, 110' are sandwiched between portions of the nacelles 102a, 102b, 102c. In another embodiment, the float / drive arms 110, 110' may be external components on the starboard and port sides (i.e., the float / drive arms 110, 110' connect to the outside of the pontoons 60).

[0052] The present disclosure also contemplates a method of generating electricity comprising providing any of the novel wave energy converters described above and operating the wave energy converter in a wave field. As described above, movement of the first body and the second body generates energy in one or more power take-off devices housed within the nacelle.

[0053] It should be appreciated that the WEC 100 can be configured to be free-floating or moored. Those skilled in the art will appreciate that in one embodiment, the WEC 100 is configured to be moored and includes a mooring system including one or more mooring lines that may be connected to a mooring base and / or an umbilical base (not shown). In one embodiment, the mooring system includes a mechanism for lengthening or shortening at least one mooring line.

[0054] The WEC can be towed along the water surface to its desired location. Once the WEC reaches the desired location, the ballast tanks 50 and / or spars 104, 106 can be flooded with water to submerge the WEC to its operational state. As described above, the ballast tanks serve as the primary mass element of the primary body and can be filled with materials such as, but not limited to, water, sand, concrete, and / or PERMA BALLAST® to submerge the primary body to its operational state. In one embodiment, the ballast can be dynamic, allowing materials such as water to be pumped in and out of specific compartments to improve performance. In one embodiment, dynamic ballast can be used to fine-tune the WEC to specific wave conditions.

[0055] While several embodiments of the present invention have been described and illustrated herein, those skilled in the art will readily conceive of various other means and / or structures for performing the functions and / or results and / or obtaining one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Accordingly, it should be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described and claimed. The present invention relates to each individual feature, system, article, material, and / or method described herein. Additionally, any combination of two or more such features, systems, articles, materials, and / or methods is included within the scope of the invention, provided that such features, systems, articles, materials, and / or methods are not mutually inconsistent.

[0056] All definitions defined and used herein should be understood to govern dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0057] The indefinite articles "a" and "an," as used in the specification and claims, unless expressly stated to the contrary, should be understood to mean "at least one."

[0058] The term "and / or," as used in this specification and in the claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements conjunctively present in some cases and alternatively present in other cases. Other elements other than those specifically identified by the "and / or" clause may be optionally present, whether or not related to those specifically identified elements, unless expressly stated to the contrary.

[0059] All literature, patents and patent applications, and publications cited or referred to in this application are hereby incorporated by reference in their entirety.

Claims

1. 1. A wave energy conversion device comprising: a nacelle having a starboard side and a port side, the nacelle housing a power take-off; at least one buoyant member coupled to the nacelle; a ballast tank coupled to the nacelle, the ballast tank, the at least one buoyancy member, and the nacelle together forming a first body, the first body coupled to the power take-off device; a float and a drive arm forming a second body, the second body being rotatably connected to the first body about a connecting shaft, the second body being connected to the power take-off device; Equipped with A wave energy conversion device wherein the second body is configured to rotate relative to the first body about the connecting axis within a radial span bounded by the proximal end of the float and the radially distal end of the float.

2. 2. A wave energy converting apparatus as described in claim 1, wherein the at least one buoyant member includes a first buoyant member coupled to a starboard side of the nacelle and a second buoyant member coupled to a port side of the nacelle.

3. 3. A wave energy converting apparatus as claimed in claim 2, wherein the first buoyant member and the second buoyant member each have a substantially cylindrical body.

4. 3. A wave energy converter as described in claim 2, wherein the first body further comprises a nacelle tube having a first end extending outwardly from a starboard side of the nacelle and a second end extending outwardly from a port side of the nacelle, the first buoyant member being coupled to the first end of the nacelle tube and the second buoyant member being coupled to the second end of the nacelle tube.

5. a first spar extending downwardly from the first buoyancy member to the ballast tank; a second spar extending downwardly from the second buoyancy member to the ballast tank; and 5. A wave energy converting apparatus as claimed in claim 4, wherein the nacelle tube, the first buoyant member and the first spar are connected to each other at a first junction, and the nacelle tube, the second buoyant member and the second spar are connected to each other at a second junction.

6. 5. A wave energy converting apparatus as claimed in claim 4, wherein a first end of the nacelle tube is connected to a forward end of the first buoyant member and a second end of the nacelle tube is connected to a forward end of the second buoyant member.

7. 2. A wave energy converter according to claim 1, wherein the nacelle, the at least one buoyant member, the ballast tank and the float each have a substantially cylindrical body.

8. 2. A wave energy converting apparatus as claimed in claim 1, wherein the first body has a centre of mass and a centre of buoyancy, and the connecting axis is offset from a line formed between the centre of mass and the centre of buoyancy of the first body.

9. 2. A wave energy converting apparatus according to claim 1, wherein the nacelle has a longitudinal axis and the connecting axis is aligned with the longitudinal axis of the nacelle.

10. 2. A wave energy converter as described in claim 1, wherein the power take-off device is a direct drive generator having a rotor assembly and a stator assembly, the second body being operably connected to the power take-off device rotor assembly and the first body being fixed to the power take-off device stator assembly.

11. 2. A wave energy converting apparatus according to claim 1, wherein the second body further comprises an idler arm rotatably connecting the float to the nacelle.

12. 5. A wave energy converter as described in claim 4, wherein the drive arms include a first drive arm and a second drive arm, both of the first and second drive arms rotatably connecting the float to the nacelle tube, and the second body is operably connected to the power take-off device via both the first and second drive arms.

13. 13. A wave energy converting apparatus according to claim 12, wherein the power take-off devices include a first power take-off device and a second power take-off device, the second body being operably connected to the first power take-off device via the first drive arm and the second body being operably connected to the second power take-off device via the second drive arm.

14. 14. A wave energy converter as claimed in claim 13, wherein the first and second power take-off devices are each direct drive generators having a rotor assembly and a stator assembly, the rotor assemblies of the first and second power take-off devices rotating about the connecting shaft.

15. 13. A wave energy converting apparatus according to claim 12, wherein the power take-off devices include a first plurality of power take-off devices and a second plurality of power take-off devices, the second body being operably connected to the first plurality of power take-off devices via the first drive arm and the second body being operably connected to the second plurality of power take-off devices via the second drive arm.

16. 1. A wave energy conversion device comprising: a nacelle having a starboard side and a port side, the nacelle housing a power take-off; at least one buoyant member coupled to the nacelle; a ballast tank coupled to the nacelle, the ballast tank, the at least one buoyancy member, and the nacelle together forming a first body, the first body coupled to the power take-off device; a float and a drive arm forming a second body, the second body being rotatably connected to the first body about a connecting axis, the second body being connected to the power take-off device; the second body is configured to rotate relative to the first body about the connecting axis within a radial span bounded by a proximal end of the float and a radially distal end of the float; 10. A wave energy converting device wherein the first body has a centre of mass and a centre of buoyancy, and the connecting axis is offset from a line formed between the centre of mass and the centre of buoyancy of the first body.

17. 17. A wave energy converting apparatus as described in claim 16, wherein the first body further comprises a nacelle tube having a first end extending outwardly from a starboard side of the nacelle and a second end extending outwardly from a port side of the nacelle.

18. A method for generating electricity, comprising: a) providing a wave energy converter, said wave energy converter comprising: a nacelle having a starboard side and a port side, the nacelle housing a power take-off; at least one buoyant member coupled to the nacelle; a ballast tank coupled to the nacelle, the ballast tank, the at least one buoyancy member, and the nacelle together forming a first body, the first body coupled to the power take-off device; a float and a drive arm forming a second body, the second body being rotatably connected to the first body about a connecting shaft, the second body being connected to the power take-off device; Equipped with the second body is configured to rotate relative to the first body about the connecting axis within a radial span bounded by a proximal end of the float and a radially distal end of the float; b) operating the wave energy converting device in a wave field; A method of generating electricity comprising:

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