Abstract:
An apparatus and method for converting wave energy using the relative rotational movement between two interconnected float assemblies and the relative rotational movement between each of the float assemblies and a spar which extends from a buoyant nacelle having a central longitudinal axis wherein the floats are nestable behind the buoyant nacelle.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to converting wave surge and heave into energy and more particularly to wave energy conversion (WEC) devices, systems, and methods. 
         [0003]    2. Discussion of Background Information 
         [0004]    Ocean energy, and wave energy in particular, represents a consistent, reliable and predictable energy resource that is widely-available, close to population centers and load-matched. Approximately seventy percent (70%) of the population of the entire world lives within two hundred miles of an ocean, making that an accessible source of renewable energy. Environmentally, waves also represent one of the most benign sources of clean renewable energy. This set of characteristics is unique to wave energy amongst the most widely-available, global renewable energy resources. 
         [0005]    The International Energy Agency has declared a 2030 goal for wave, tidal and other marine energy sources of the creation of 160,000 direct jobs and a savings of 5.2 billion tons of CO2 emissions. For the U.S. specifically, the electricity practically available from wave power is about 252 TWh/yr or approximately 6.5% of US electricity demand. 
         [0006]    Wave energy is a globally-desirable resource and has the potential to be a cost-competitive and important component of a diverse mix of clean, renewable energy resources. However, no company has yet been able to cost-effectively demonstrate use of the oceans&#39; slow speeds and massive hydrodynamic forces. This problem stems from a variety of considerations, including that existing wave energy conversion devices typically lack adequate protection mechanisms from extreme conditions, suffer from relative mechanical unreliability, and fail to fully capture the rotational energy of a wave. Solving the conflicting problems of survivability and cost of energy is achievable, yet success in doing so requires a significant improvement over the state-of-the-art (STOA). 
         [0007]    A need therefore exists for a wave energy conversion apparatus that efficiently and cost-effectively converts the rotational ocean wave energy into rotary motion for use in direct drive rotary generation while achieving improved reliability and survivability. 
       SUMMARY OF THE INVENTION 
       [0008]    The present disclosure describes a wave energy converter (WEC) for use in range of autonomous and grid-connected applications, including but not limited to low-power sensors, marine vehicles and vessels, desalination, aquaculture, offshore oil &amp; gas platforms, and utility-scale grid connection. The WEC is a floating, self-referenced multi-body system having at least two floats, two spars extending downward, and at least one nacelle buoyantly supportable on a surface of a body of water that effectively and efficiently converts the heave and surge of offshore swells and storm waves into rotational torque that may drive both conventional and large-diameter slow-speed direct-drive generators or pumps. 
         [0009]    The WEC does not rely on a mooring system to produce torque, but may include a mooring system for station-keeping and, in some embodiments, for directional control. In certain autonomous applications the WEC may not require a mooring at all. WECs in accordance with the present disclosure may take advantage of the rotational nature of ocean waves to capture the incident energy with floats that are rotationally coupled to produce mechanical torque in the central housing. This approach is both more efficient and better able to handle the extreme range of power found in the ocean. Such an approach may also result in safe operation over the full spectrum of weather conditions and is thus survivable in even “hundred-year storm” conditions 
         [0010]    The ultimate aim of a wave energy conversion device (WEC) is to convert one form of energy into another; in this case, in a chain including hydrodynamic conversion to mechanical torque and ultimately to electrical or other readily transportable forms. Due to the nature of the energy resource, WEC&#39;s necessitate a unique set of design requirements including: extremely low speed; extremely high force; cyclic, abrupt and chaotic motion; and peak speeds and forces that are over 10× the annual average. The extremely low speeds can be utilized to achieve a design advantage that provides a cost-effective, combined electro-mechanical solution; one that cannot be realized with conventional approaches that normally operate at 10× higher speeds. This results in lower electromagnetic hardware costs, improved efficiency, increased energy output and lower cost of energy (CoE). 
         [0011]    The wind industry has demonstrated that large-diameter direct-drive is a viable technical approach at slow speeds, and the WEC can do so as well with adjustment for the challenges presented by taking power off at extremely low speeds. Therefore, various embodiments may utilize direct drive, thereby eliminating the need for a gearbox, improving reliability, and reducing the need for expensive marine maintenance operations. In addition, the stator/rotor components may, in some embodiments, be modular, further facilitating lower pre-deployment transportation costs due to smaller overall dimensions. Modularity may also allow for “at sea” maintenance and fault tolerance. 
         [0012]    In one aspect, a system and apparatus for a wave energy converter (WEC) is provided comprising a buoyant nacelle having a central longitudinal axis. The WEC further comprises a first spar and a second spar, each mated to the buoyant nacelle. A first float may be operatively coupled to a first power take off and be positioned to rotate about the central longitudinal axis within a radial span bounded by an outer surface of the nacelle and a radially distal end of the first float and a second float may be operatively connected to a second power take off or the first power take off positioned to rotate about the longitudinal axis within a radial span bounded by a radially distal end of the first float and a radially distal end of the second float. 
         [0013]    In another aspect, a method for generating power is provided comprising a first step of providing a WEC comprising a buoyant nacelle having a central longitudinal axis, a first spar and a second spar, each mated to the buoyant nacelle, a first float, and a second float. The First float may be operatively coupled to a first power take off and positioned to rotate about the central longitudinal axis within a radial span bounded by an outer surface of the nacelle and a radially distal end of the first float, and the second float may be operatively connected to a second power take off or the first power take off and positioned to rotate about the longitudinal axis within a radial span bounded by a radially distal end of the first float and a radially distal end of the second float. The method for generating power also comprises a second step of deploying the WEC in a wave field. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    One will better understand these and other features, aspects, and advantages of the present invention following a review of the description, appended claims, and accompanying drawings in which: 
           [0015]      FIGS. 1A-E  are 3D isometric, external views illustrating a WEC in accordance with various embodiments of the present invention. 
           [0016]      FIGS. 1F-G  are side views illustrating arched drive arms in accordance with various embodiments of the present invention. 
           [0017]      FIGS. 2A-B  are cross-sectional top-views illustrating interior components of a WEC in accordance with various embodiments of the present invention. 
           [0018]      FIGS. 3A-D  are side views illustrating WECs having hydrodynamic control systems positioned at various depths along spars of various lengths in accordance with various embodiments of the present invention. 
           [0019]      FIG. 4  is a cross-sectional front-view of a WEC illustrating various ingress/egress and access features in accordance with various embodiments of the present invention. 
           [0020]      FIG. 5  is an illustration of particle velocities in a wave field in accordance with various embodiments of the present invention. 
           [0021]      FIG. 6  is an exaggerated illustration of the orbital motion of a WEC in accordance with various embodiments of the present invention. 
           [0022]      FIG. 7  is an illustration of the orbital motion of a WEC and the wave response motion of the first float and second float in accordance with various embodiments of the present invention. 
           [0023]      FIGS. 8A-F  are illustrations of various mooring systems attached to WECs in accordance with various embodiments of the present invention. 
           [0024]      FIGS. 9A-F  are side views illustrating an overtopped float correction in accordance with various embodiments of the present invention. 
           [0025]      FIGS. 10A-D  are top and side views of nested and/or deployed WECs in accordance with various embodiments of the present invention 
           [0026]      FIG. 11  provides side views illustrating the length and depth of four exemplary WECs in accordance with various embodiments of the present invention. 
           [0027]      FIGS. 12A-C  are dimensional schematics of a small-scale WEC in accordance with various embodiments of the present invention. 
           [0028]      FIGS. 13A-C  are dimensional schematics of a moderate-scale WEC in accordance with various embodiments of the present invention. 
           [0029]      FIGS. 14A-C  are dimensional schematics of a large-scale WEC for deployment in moderately active wave fields in accordance with various embodiments of the present invention. 
           [0030]      FIGS. 15A-C  are dimensional schematics of a large-scale WEC for deployment in highly active wave fields in accordance with various embodiments of the present invention. 
           [0031]      FIG. 16  is a flowchart illustrating a method in accordance with various embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    The technology of the present disclosure relates to a wave energy converter (WEC) useful for transforming the energy associated with the heave and surge of offshore swells and storm waves into rotational power. Turning now to  FIGS. 1A-G , the WEC  100  comprises a buoyant nacelle  102  having a central longitudinal axis, a first spar  104 , a second spar  106 , a first float  108  operatively coupled (e.g., by first float drive arms  112 ) to a power take off (PTO) and a second float  110  operatively coupled (e.g., by second float drive arms  114 ) to a power take off (e.g., the first power take off or a second power take off). In some embodiments the WEC  100  may also include a hydrodynamic control system  116  (HCS). 
         [0033]    In some embodiments, the nacelle  102  may be described as a substantially watertight housing within which may be housed one or more rotary-driven power take offs. In other embodiments the nacelle may be described as two or more (e.g., three as shown) connected, substantially watertight modules  118 ,  120 ,  122 . In some such embodiments, a center module  122  may be an empty buoyant shell, which may contain power generation, maintenance, and/or other equipment, or may be used for any other suitable purpose. In further such embodiments, a first module  118  and a second module  120  each houses one or more rotary-driven power take offs. 
         [0034]    Modularization and/or compartmentalization of any WEC  100  component (e.g., spars  104 ,  106 , floats  108 ,  110 , nacelle  102 , etc.) may be desirable in many embodiments. Compartmentalization may, for example, provide a mechanism to contain potential leaks, such that, in the event of a leak, any flooding is contained to a limited area of the WEC  100 . Compartmentalization also provides various discreet areas for more useful equipment storage spaces, more accessible maintenance areas, to serve as dynamic ballasting tanks, etc. Modularization of any particular WEC  100  component may provide the additional benefits of reduced size during transport and/or simplifying at-sea maintenance, each of which reduces costs and operational downtime. 
         [0035]    The nacelle  102  may be produced from composite material (e.g., carbon fiber, Kevlar, fiberglass, etc.), concrete, rolled steel, aluminum, and/or any other suitable metal or alloy. In some embodiments, any of the nacelle  102  or modules thereof  118 ,  120 ,  122  may include nacelle access hatches  126  for loading/offloading equipment and personnel (e.g., for maintenance and repairs). As discussed in more detail below with reference to  FIGS. 2A-B , buoyant floats  108  and  110  are operatively coupled to the one or more PTOs mounted within the nacelle  102 . The operative coupling may, in some embodiments, comprise drive arms  112 ,  114  connected to, for example, a drive shaft/hub extending into the nacelle  102  or a gearbox connected to such a drive shaft/hub. A drive shaft/hub according to some embodiments may in turn be connected to, for example, one or more direct drive generator(s), gearbox drive generator(s), hydraulic system(s), pumping system(s), water pump(s), water desalinator(s), pneumatic pump(s), hydraulic pump(s), etc. However, it will be understood that, in view of this disclosure, one skilled in the art may readily design alternatives to the above for transferring rotary power to a PTO mounted within a nacelle and that these embodiments are within the scope of this disclosure. 
         [0036]    Other structural elements of a WEC  100  in accordance with the present disclosure may include a first spar  104  and a second spar  106 . A spar (e.g.,  104 ,  106 ), as that term is used herein, comprises a hollow or solid elongate element. A 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 produced from composite material (e.g., carbon fiber, Kevlar, fiberglass, etc.), concrete, rolled steel, aluminum, and/or any other suitable metal or alloy. Depending on scale, one or more of the spars  104 ,  106  may be hollow, compartmentalized, or modularized to house or provide ingress/egress for ballast, equipment, and personnel associated with power generation, maintenance, ballasting etc. When deployed, the first spar  104  and second spar  106  extend downward into a body of water. The spars  104 ,  106  may generally be attached, directly or indirectly, to opposing ends of the nacelle  102 . In some embodiments, the spars  104 ,  106  may be fixedly or rotatably attached to the nacelle  102 , however, it will be clear in view of this disclosure that any suitable method of attachment may be used. 
         [0037]    In some embodiments one or more of the spars  104 ,  106  can extend upward from the nacelle to operate as a mooring mast or accessory (e.g., antenna, solar panel, warning light, etc.) mounting structure. Various embodiments may include boarding areas (e.g., service platforms and/or docking fixtures) attached to one or more of the spars  104 ,  106 , providing for improved service access for deployed WECs  100 . For larger designs, including utility scale designs, a spar access hatch  128  may be provided in the upper region of an extended spar. Spar access hatches  128  will generally be above water line in non-storm conditions and designed such that maintenance personnel and/or equipment can enter/exit the WEC  100  to gain further access to the components and interior equipment of the WEC  100 . 
         [0038]    The spars  104 ,  106  provide structural support to the WEC  100  and provide a design tool for setting a center of gravity (CG) and/or center of buoyancy (CB) of the WEC  100 . The CG and/or CB design point can be achieved by tailoring spar length (draft), spar weight, and/or spar weight distribution to particular applications. Additionally, the spars  104 ,  106  serve as a point of attachment for one or more hydrodynamic control systems  116  (e.g., a weight, plate, or ballast tank). 
         [0039]    In some embodiments, a HCS  116  may be fixedly attached to the spars  104 ,  106 . In other embodiments, as further described below with reference to  FIGS. 3A-D , the HCS  116  may be movably mounted to the spars  104 ,  106  such that the position of the HCS  116  along the spars  104 ,  106  can be varied. It may be desirable to adjust the position of the HCS  116  for any number of reasons, including but not limited to, variation in sea states, variation in weather, and/or changes to mission requirements. HCSs  116  may include, but are not limited to, plates (e.g., heave plates, damper plates), shaped members (e.g., wedges, cylinders, cubes, ellipses, etc.), ballast tanks, hydrodynamic (e.g., airfoil shaped) plates and/or ballast tanks, etc. HCSs may be produced from composite material (e.g., carbon fiber, Kevlar, fiberglass, etc.), concrete, rolled steel, aluminum, and/or any other suitable material. In some embodiments, such HCSs  116  may include additional features (not shown) such as, for example, dynamic ballast controls, vanes/rudders, trim tabs, mooring system attachments, or any other desired additional feature. It will be apparent in view of this disclosure that any WEC  100  component (e.g., spars  104 ,  106 , floats  108 ,  110 , nacelle  102 , etc.), or a combination of such components, may, in various embodiments, include one or more of the features as described above with reference to an HCS  116 . It will be further apparent in view of this disclosure that, in some embodiments, any such features or combination of such features may be attached to the WEC  100  directly or as part of an external module/compartment rather than being included as part of any particular component of the WEC  100   
         [0040]    While depicted as a single HCS  116  being attached to two spars  104 ,  106 , it will be apparent in view of this disclosure that any number of HCSs  116  may be directly or indirectly attached by any means to any component, or combination of components, of the WEC  100  (e.g., floats  108 ,  110 , drive arms  112 ,  114 , nacelle  102 , etc.). For example, some embodiments may have two independently movable HCSs  116 , each mounted to one spar (e.g.,  104  or  106 ). In other embodiments, a HCS may be indirectly attached to the spars  104 ,  106  via a flexible member (e.g., cable, rope, chain, or any other tethering device). 
         [0041]    An important feature of various WECs  100  in accordance with the present disclosure may be the arrangement of the two or more floats  108 ,  110 . More specifically, unlike prior art embodiments, the present disclosure relates to a WEC  100  having a first float  108  and a second float  110 , each designed to rotate about a central longitudinal axis of the nacelle  102 . In various embodiments the first float  108  and the first float drive arms  112  are designed to rotate outside the nacelle  102  within a radial span region defined by the second float  110  and the second float drive arms  114 . Accordingly, in such embodiments, the float arrangement design allows both the first float  108  and the second float  110  to achieve uninhibited, 360-degree rotation about the central longitudinal axis. The advantages associated with this design with regard, for example, to efficiency and survivability will be discussed in greater detail below with reference to  FIGS. 14A-F . 
         [0042]    It will be apparent in view of this disclosure that the arrangement depicted in  FIGS. 1A-G  of the floats  108 ,  110  and drive arms  112 ,  114  being positioned within the spars  104 ,  106  is not exclusive. In various embodiments the floats  108 ,  110  may each be wider than, and connect to the PTO(s) outside of, the spars  104 ,  106 . In some such embodiments, the drive arms  112 ,  114  may be longer than the spars such that each float  108 ,  110  retains uninhibited, 360-degree rotation about the central longitudinal axis. In further embodiments the first float  108  and first float drive arms  112  may be positioned within the spars  104 ,  106  as depicted in  FIGS. 1A-G  while the second float  110  and second float drive arms  114  are positioned outside of the spars  104 ,  106  as described above. The term drive arms (e.g.,  112 ,  114 ) as described herein includes float connecting arms directly and operatively connected to a drive shaft/hub, but may also include float connecting arms designed to idle about a shaft or structural member as described in greater detail below with reference to  FIGS. 2A-B . As shown in  FIGS. 1F-G , the drive arms  112 ,  114  need not be straight, but may, in some embodiments, be curved or arched. However, it will be understood that drive arms  112 ,  114  in accordance with the present disclosure may have any shape and/or cross-section. 
         [0043]    It will be further apparent in view of this disclosure that the “nested” arrangement of the first float  108  and second float  110  and their respective drive arms  112 ,  114  can be extended to designs comprising more than two floats rotating about, and operatively connected to a single nacelle (e.g., two floats positioned within the spars as depicted in  FIGS. 1A-G  and additional floats positioned outside the spars as described above). Similarly, one skilled in the art could readily make and use a wave energy converter comprising an array of connected wave energy converters (e.g., having a spar-nacelle-spar-nacelle-spar arrangement with nested float pairs attached to each nacelle). Such array embodiments may facilitate mooring, construction cost, and maintenance efficiencies by reducing the number of spars required per nacelle, sharing mooring systems, and reducing the number of generation sites to be maintained. 
         [0044]    The floats  108 ,  110  may be produced from composite material (e.g., carbon fiber, Kevlar, fiberglass, etc.), rolled steel, aluminum, any other metal or alloy, wood, foam, rubber, concrete, and/or any other suitable material. Floats of any size, shape, volume, buoyancy, weight, and/or orientation may be used in accordance with the present disclosure. In various embodiments one or more of the floats  108 ,  110  may be designed to have one or more internal ballast tanks (not shown). In some such embodiments, the internal ballast tanks may be dynamic ballast tanks, adjustable for tuning purposes, damage prevention, maintenance, towing, overtopping correction, or any other circumstance that may require repositioning, buoyancy corrections, or other adjustments to the floats  108 ,  110 . 
         [0045]    In some preferred embodiments, each float may be designed to optimize cost-effective energy capture. In various embodiments the first float  108  may have an upper side  108   a , a forward side  108   b , and an aft side  108   c . The upper side  108   a  and aft side  108   c  of the first float  108  may be designed to minimize materials (i.e., reduce costs) used to enclose the structure. For example; a semicircular upper side  108   a  requires more material and increases costs of production. All sides (e.g.,  108   a - c ) of first float  108  may be flat or concave, but in some preferred embodiments may be slightly convex. Such slightly convex curvature allows for composite manufacture on a wound mandrel as well as mold-based composite manufacture processes. 
         [0046]    The forward side  108   b  may, in some embodiments, be optimized in both radius and slope in order to maximize energy capture from the incident wave climate. Such optimization may be achieved using hydrodynamic numerical analysis and optimization techniques to design the float to maximize power delivered by the first float  108  while minimizing the material utilized. In such embodiments the optimized shape (slope and radius) is the result of an optimized power to cost ratio. It will be apparent in view of this disclosure that particular float geometries, dimensions, and orientations will vary depending on the particular size, power requirements, and expected operating conditions of each individual WEC  100 . In a plan view perspective, the forward side  108   b  of the first float  108  is rectangularly shaped to maximize exposed surface area, thereby increasing energy capture. Additionally, the top side float volume, or freeboard, is optimized to the minimal necessary volume (i.e., reduced freeboard) to allow sufficient driving force while eliminating excess reserve buoyancy to improve survivability. This contributes to a continued operation of the WEC  100  in all wave conditions (including storm waves) by removing excess force that would otherwise be created by excess freeboard. 
         [0047]    The second float  110  may also be of any size, shape, volume, buoyancy, weight, and/or orientation in accordance with the present disclosure. In some preferred embodiments, each float may be designed to optimize cost-effective energy capture. In various embodiments the second float  110  may have an upper side  110   a , a forward side  110   b , and an aft side  110   c . The second float  110  is designed in some embodiments to have a deeper draft than the first float  108 . The draft may be chosen to be any depth, but in some embodiments may be optimized to maximize a surface area which is in contact with the wave and/or optimized to maximize the combined effects of wind, waves, and currents. Maximizing contact surface area may increase energy capture when the wave force acts against the second float  110 . The upper side  110   a  and aft side  110   c  of the second float  110  may be designed to minimize materials (i.e., reduce costs) used to enclose the structure. For example; a semicircular upper side  110   a  requires more material and increases costs of production. All sides (e.g.,  110   a - c ) of second float  110  may be flat or concave, but in some preferred embodiments may be slightly convex. Such slightly convex curvature allows for composite manufacture on a wound mandrel as well as mold-based composite manufacture processes. 
         [0048]    The forward side  110   b  may, in some embodiments, be optimized in both radius and slope in order to maximize energy capture from the incident wave climate. Such optimization may be achieved using hydrodynamic numerical analysis and optimization techniques to design the float to maximize power delivered by the second float  110  while minimizing the material utilized. In such embodiments the optimized shape (slope and radius) is the result of an optimized power to cost ratio. It will be apparent in view of this disclosure that particular float geometries, dimensions, and orientations will vary depending on the particular size, power requirements, and expected operating conditions of each individual WEC  100 . In a plan view perspective, the forward side  110   b  of the second float  110  is rectangularly shaped to maximize exposed surface area, thereby increasing energy capture, and optimized to maximize the combined effects of wind, waves, and currents. Additionally, the top side float volume, or freeboard, is optimized to the minimal necessary volume (i.e., reduced freeboard) to allow sufficient driving force while eliminating excess reserve buoyancy to improve survivability. This contributes to a continued operation of the WEC  100  in all wave conditions (including storm waves) by removing excess force that would otherwise be created by excess freeboard. 
         [0049]    In various embodiments, the optimized shape of the second float  110  is similar in outer contour to that of the first float  108 . In some such embodiments, this similarity allows for both the first float  108  and second float  110  to be made from the same mold and manufacturing process, thereby eliminating the need for multiple sets of manufacturing equipment and further reducing manufacturing costs. To utilize a first float  108  as a second float  110 , the first float  108  may be flipped from port to starboard and rotated toward the bottom. This allows for both forward sides  108   a  and  110   a  to achieve optimized wave energy capture, the aft float to have a deeper draft, and enables cost reductions by making both floats from a single mold. 
         [0050]    As described above, the floats  108 ,  110  are operatively connected to PTOs mounted within the nacelle  102 . Such PTOs may, in some embodiments, comprise one or more direct drive generator(s), gearbox drive generator(s), hydraulic system(s), pumping system(s), water pump(s), water desalinator(s), pneumatic pump(s), hydraulic pump(s), etc. For various pump and hydraulic-related embodiments, the drive shaft/hub may be directly or indirectly connected to, for example an impeller, compressor rotor, and/or mechanical turbine rotor. In some electrical generation embodiments the drive shaft/hub may be directly or indirectly connected to, for example, one or more rotors and/or stators. However, it will be understood, in view of this disclosure, that many design alternatives to the above exist for PTO components mounted within a nacelle and that these alternatives are within the scope of this disclosure. 
         [0051]      FIG. 2A  provides a cross-sectional top-view of the nacelle  102 , focusing on a first module  118  and  FIG. 2B  provides a cross-sectional top-view of the nacelle  102  focusing on a second module  120 . In the embodiment depicted in  FIGS. 2A-B , each of first module  118  and second module  120  is connected to a central module  122  and mounted over a spar-nacelle connection member  201 . In some embodiments, the first module  118  and the second module  120  each contains a rotary-driven PTO. In power generation applications, such rotary-driven PTOs may include one or more rotors  204 , which are rotatable in relation to one or more stators  206 . Depending on the application, stators  206  may be independently rotatable or retained in a fixed rotational position relative to the nacelle  102 . Relative rotation between the rotors  204 , stators  206 , spar-nacelle connection member  201 , and/or the module  118 ,  120  within which the PTO is housed may be achieved by way of drive bearings  208 , or any other bearing or similar mechanism which allows one or more components to freely rotate about or within another component. 
         [0052]    In some embodiments, one or more rotors  204  may be integrated with a direct-drive shaft/hub  202 ,  203 . In other embodiments, and as shown in  FIGS. 2A-B , a drive shaft/hub  202 ,  203  may be connected to a radial extension  220 , which is connected, via a rotor interface structure  216 , to one or more rotors  204 . However, it will be apparent in view of this disclosure that rotors  204  may be operatively connected to any drive shaft/hub  202 ,  203  via any other suitable means, including but not limited to, a gearbox or transmission, bolt-on, etc. 
         [0053]    In various embodiments, one or more stators  206  may be fixedly or rotatably attached to an outer nacelle  102  and/or module  118 ,  120  via a stator interface structure  218 . The rotor interface structure  216  and stator interface structure  218  may, in some embodiments be designed to control an air gap between rotors  204  and stators  206 . Such interface structures  216 ,  218  may include, for example, retention slots, weld joints, braze joints, interference flanges, bolted or riveted flanges, mechanical rails, magnetic rails, or any other suitable gap control structure. 
         [0054]    The drive shaft/hub  202 ,  203  may generally rotate about the spar-nacelle connection member  201  on drive bearings  208  or other suitable structures. In various embodiments, the drive shaft/hub  202 ,  203  may be sealed to the module  118 ,  120  and/or the spar-nacelle connection member  201  by one or more shaft seals  212  to prevent the intrusion of seawater and/or harmful foreign objects/debris. 
         [0055]    The first float drive shaft/hub  202  may be operatively connected to a first float drive arm  112  adjacent the first module  118  while a second float drive arm  114  adjacent the first module  118  may be idle and freely rotatable about the spar-nacelle connection member  201  on a second float idle bearing  214 . In various embodiments where allowing uninhibited 360-degree rotation of the floats  108 ,  110  is desirable, the second float drive shaft/hub  203  may be operatively connected to a second float drive arm  114  adjacent the second module  120  while a first float drive arm  112  adjacent the second module  120  may be idle and freely rotatable about the second float drive shaft/hub  203  on a first float idle bearing  215 . In such embodiments, employing this asymmetrical design may enable the positioning of first float drive arms  112  and first float  108  within the region defined by second float drive arms  114  and second float  110  as described above with reference to  FIGS. 1A-G . 
         [0056]    While  FIGS. 2A-B  depict a WEC  100  having two PTOs, it will be apparent in view of this disclosure that any number of PTOs may be used. In various embodiments having a single PTO, the first float  108  may connect to the rotors  204 , and the second float may connect to the stators  206 , which may be rotatable stators. It will be further apparent in view of this disclosure that, although the rotors  204  are shown to be configured internal to fixed outer stators  206 , the rotors  204  could be configured as outer rotors around fixed inner stators, or both the rotors  204  and stators  206  could be rotatable regardless of positioning. 
         [0057]    In some embodiments, including the embodiment depicted in  FIGS. 2A-B , the rotary-driven PTOs may be large-diameter direct-drive systems, (e.g., low-speed, high torque systems). Such systems have proven to represent a viable technical approach in connection with harnessing wind energy and the same slow-speed principles apply in the marine context. However, the technology described herein may be implemented using rotary-driven PTOs of any type, including, but not limited to, generator(s), gearbox and generator(s), hydraulics and generator(s), water pump(s), and/or any other suitable rotary PTO device. 
         [0058]    Various embodiments in accordance with the present disclosure may include a hydrodynamic control system  116  (HCS) as described above.  FIGS. 3A-D  are side views of a WEC  100  in accordance with the present disclosure having HCSs  306 ,  308  positioned in varying locations along spars  302 ,  304  of various lengths.  FIG. 3D  shows HCS  308  fixedly attached to a relatively long spar  304 .  FIGS. 3A-3C  illustrate a movable HCS  306  in various positions along the spar  302 . Any mechanism (not shown) may be used to adjust the position of the hydrodynamic control system. Such mechanisms may, in some embodiments, be motorized drives. In other embodiments, there may be no motorized drives and HCS  306  may include a dynamic ballast control and a braking system for engagement with the spar. In such embodiments the HCS  306  may, for example, be repositioned along the spar  302  by releasing a brake, adjusting a ballast to buoyantly reposition the HCS  306 , and engaging the brake to retain the repositioned HCS  306  in place. It will be apparent in view of this disclosure that the examples described above are not limiting, and that any number or combination of suitable adjustment mechanisms may be used with WECs  100  designed in accordance with the present disclosure. 
         [0059]    As described above with reference to  FIGS. 1A-G , various embodiments may include boarding areas (e.g., service platforms and/or docking fixtures) attached to one or more of the spars  104 ,  106  and/or nacelle  102  as well as, for some embodiments, nacelle access hatches  126  and/or spar access hatches  128  for improved service access for deployed WECs  100 . Access hatches  126 ,  128  may generally be provided in the upper region of a nacelle  102  or an extended spar such that the access hatches  126 ,  128  are generally above the water line in non-storm conditions. Such access hatches may also be generally designed such that maintenance personnel and/or equipment can enter/exit the WEC  100  to gain further access to the components and interior equipment of the WEC  100 . 
         [0060]    Referring now to  FIGS. 1A-G  and  FIG. 4 , in some embodiments, ingress/egress of equipment, ballast and/or personnel to a WEC  100  may be provided via nacelle access hatches  126 , spar access hatches  128 , and/or any other hatch or airlock positioned on an exterior of any other component of the WEC  100 . Nacelle access hatches  126  may provide access to the interior of a module  118 ,  120 ,  122 , which may or may not house a PTO. Internal access hatches  402  and internal passageways  403  may, in some embodiments, provide access to other components of the WEC  100 . Where vertical movement is desirable, interior nacelle ladders  404  may be provided. It will be apparent in view of this disclosure that, while ladders are depicted herein, any suitable vertical transport device (e.g., escalators, elevators, lifts, dumbwaiters, etc.), or even no vertical transport device at all, may be used in accordance with the present disclosure and may, for some embodiments, be preferred. 
         [0061]    Spar access hatches  128  may provide access to the interior of a spar  104 ,  106 . In some embodiments, boarding areas, (e.g., service platforms and/or docking fixtures) may be affixed to the exterior of one or more spars  104 ,  106  to provide an easier approach to the spar access hatches  128 . Internal spar ladders  406  provide for vertical movement within the spar. However, while ladders are depicted herein, it will be apparent in view of this disclosure that any suitable vertical transport device (e.g., escalators, elevators, lifts, dumbwaiters, etc.), or even no vertical transport device at all, may be used in accordance with the present disclosure and may, for some embodiments, be preferred. Likewise, in horizontal passageways, railed overhead cranes or rigs (block &amp; tackle, etc.), conveyor belts or rollers, etc. may be used in accordance with the present disclosure and may, for some embodiments, be preferred. 
         [0062]    A movement in water of a WEC  100  designed in accordance with the present disclosure is described with reference to  FIGS. 5-7 . Water velocities within a wave are illustrated in  FIG. 5 . Particle velocities in the deep water wave field exhibit maximum amplitude in all 360 degrees of direction within a plane perpendicular to the crests of the propagating waves. Two discrete directions of these water particle directions are summarily described as heave and surge, depicted in  FIG. 5 . Heave describes the vertical up and down directions in the wave field, while surge represents the horizontal direction in the wave field that is perpendicular to the crests of the incoming waves. These water particle velocity vectors are of greatest magnitude at the free surface of the water and decrease exponentially toward zero as the water depth increases, therefore the strongest body interactions occur at the free surface of the water. The axis of rotation that acts in the heave-surge plane is described as pitch. To maximize energy capture, the wave energy converter should be excitable by the maximum amplitude vector in all 360 degrees of the wave at the free surface of the water, thus a device should be free to absorb energy in the three degrees of freedom described as pitch, surge, and heave and be located at or near the water&#39;s surface. At trough  502 , water moves entirely in a reverse surge motion along a velocity gradient having a maximum velocity adjacent the surface of the water. At upward heave  504 , water moves entirely in an upward heave motion. At peak  506 , water moves entirely in a forward surge motion along a velocity gradient having a maximum velocity adjacent the surface of the water. At downward heave  508 , water moves entirely in a downward heave motion. 
         [0063]    In operation, as depicted in  FIGS. 6 and 7 , the WEC  100  is excited by the incoming waves to pitch, surge, and heave, resulting in a pitching orbital pattern described below. Shown at time T 1   602 ,  702 , the WEC  100  has moved in surge such that the spars  104 ,  106  and nacelle  102  are to the right (or aft) of center  601  and pitched clockwise. At time T 2   604 ,  704 , the spars  104 ,  106  and nacelle  102  have rotated counterclockwise in pitch to a vertical orientation and moved left (or forward) in the surge direction. At time T 3   606 ,  706 , the WEC  100  has moved in surge such that the spars  104 ,  106  and nacelle  102  are to the left (or forward) of center  601  and pitched counter clockwise. At time T 4   608 ,  708 , the spars  104 ,  106  and nacelle  102  have rotated clockwise in pitch to a vertical orientation and moved right (or aft) toward center  601  in the surge direction. These motions are exaggerated in  FIG. 6  to aid in understanding the motions and in  FIG. 7  the motions are representative of scaled motion. 
         [0064]    In practice these motions occur in a 360 degree continuum of directions that are discretely described by the heave and surge vectors discussed above. Geometric dimensioning will affect the magnitude of WEC body response to the wave excitation; for example a larger surface will experience greater force on that body than a smaller surface. Additionally a different inertia of the WEC will result in a differing delay of the WEC body response in each degree of freedom to the wave excitation. The combination of buoy shape, CG and inertia will ultimately affect the phase and amplitude of WEC response to the incoming wave.  FIG. 7  depicts the numerically computed phased response of the spars  104 ,  106  and nacelle  102  with respect to the wave for an 8.5 second wave period. Without device tuning, a differing wave period will result in differing WEC response and a different phase relationship with respect to the wave. 
         [0065]    As depicted in  FIG. 7 , a first float  108  is nominally designed to approach an incoming wave such that it is forced by the wave to rotate about the central longitudinal axis of the nacelle  102 . The first float  108  is designed to follow the wave&#39;s surface and primarily respond in phase with the wave in both heave and surge, resulting in a pitching motion of the first float  108  with respect to the nacelle  102 . These heave and pitch motions of the first float  108  result in rotation of the first float  108  about the central longitudinal axis of the nacelle  102 . The pitch motion of the nacelle  102  acts out of phase with that of the first float  108 , thus increasing the velocity of relative rotational motion between the two bodies. This relative rotational motion is depicted in time steps T 1 , T 2 , T 3 , and T 4  of  FIG. 7  as described above. 
         [0066]    As further depicted in  FIG. 7 , a second float  110  is nominally designed to approach the departing wave such that it is forced by the wave to rotate out of phase with the central longitudinal axis of the nacelle  102 . The second float  110  is designed to maximize a pitching motion of the second float  110  with respect to the nacelle  102 . These heave and pitch motions of the second float  110  result in rotation of the second float  110  about the central longitudinal axis of the nacelle  102 . The pitch motion of the nacelle  102  acts out of phase with that of the second float  110 , thus increasing the velocity of relative rotational motion between the two bodies. This relative rotational motion is depicted in time steps T 1 , T 2 , T 3 , and T 4  of  FIG. 7  as described above. The radial distance of the second float  110  from the nacelle  102  is nominally greater than that distance for the first float  108 . This distance is tunable for different site locations or wave climates. 
         [0067]    In many embodiments, it is desirable to keep the WEC  100  on station relative to a wave field, at a desired orientation relative to a wave field, and/or autonomously (i e, manned or unmanned, but not towed) move the WEC  100  between wave fields. One or more such functions may be accomplished, in various embodiments, by the inclusion of, for example, one or more mooring system(s), or one or more propulsion system(s). For embodiments including propulsion systems, the propulsion may be provided by any suitable propulsion device (e.g., propeller, pumpjet, paddle wheel, magnetohydrodynamic drive, etc.). Such propulsion systems may be mounted on any WEC  100  component (e.g., spars  104 ,  106 , floats  108 ,  110 , nacelle  102 , HCS  116 , etc.) to provide yaw control, autonomous transport between deployment sites, station keeping at a deployment site, or any other purpose for which propulsion systems may be used. 
         [0068]    Many embodiments in accordance with the present disclosure include a mooring system, which may be designed to keep the WEC  100  on station relative to a wave field (not shown) without over-ranging the electrical line  810 . The mooring system may be any of a slack, low-column, mid-column, or high-column mooring system having one or more mooring lines that attach to WEC  100 . In some embodiments, the mooring system may also be used to control yaw of the WEC  100  relative to the wave field. In such embodiments, the WEC  100  may be passively self-oriented by the mooring system  800  and/or vanes/rudders attached to the WEC  100  or may include a mechanism (not shown) such as, for example, a chain or cable winch for shortening or lengthening any of the mooring lines, thereby rotating the WEC  100 , a rotatable interface between the mooring system and the WEC  100  such that the WEC  100  rotates relative to the mooring system, or any other suitable mechanism for controlling yaw or other positioning of the WEC  100 . 
         [0069]    As shown in  FIG. 8A , a three-point mooring system  800  may be used to control directionality. As shown in  FIGS. 8B-F , two-point or one-point mooring systems  800  may also be used. Each such mooring system may be designed such that each of the horizontal mooring lines  802  joins a HCS  116  at a connection point  804 . It will be apparent in view of this disclosure, however, that one or more horizontal mooring lines  802  may be attached to any component of a WEC  100  (e.g., floats  108 ,  110 , spars  104 ,  106 , nacelle  102 , etc.). Although each of the horizontal mooring lines  802  is shown in  FIGS. 8A-F  to join the WEC  100  at an independent connection point  804 , it will be apparent in view of this disclosure that each mooring line may alternatively join the WEC  100  at a common connection point  804 . As further illustrated in  FIGS. 8A-F , each horizontal mooring line  802  may be attached to a mooring buoy  806 , which may then be connected to a vertical mooring line  808 . It will be understood in view of this disclosure that horizontal mooring line  802  and vertical mooring line  808  may be the same mooring line and connected to mooring buoy  806 . It will be further understood in view of this disclosure that the term mooring buoy  806  as used herein also includes low-column, mid-column, and high-column buoys and that such buoys may have any positive or negative buoyancy. Specifically depicted in the illustrative examples of  FIGS. 8A-F  are mid-column buoys, which may, in some embodiments, have a net positive buoyancy ranging from 10,000 lbs. to 100,000 lbs. 
         [0070]    In accordance with some embodiments,  FIG. 8F  depicts a single mooring leg approach. In such embodiments, the WEC  100  is attached at a forward region of an HCS  116  and a single mooring leg comprised of a vertical mooring line  808  or lines, a horizontal mooring line  802  or lines and a mooring buoy  806  or buoys. The mooring lines  802 ,  808  may be made of, for example, cable, nylon, polyester, chain, any other suitable material, or any combination of these. A single mooring leg of this configuration, connected to the forward region of a HCS  116  may, in various embodiments, allow for the WEC  100  to rotate and passively align to head into the oncoming wave. Numerical analysis confirms that a forward connection improves such a system&#39;s ability to passively orient into the oncoming wave. The use of different mooring line materials and different buoyancies of the mooring buoy may allow the designer to select a preferred load-displacement behavior and maximum load capabilities of the mooring leg. 
         [0071]    A single leg mooring as illustrated by  FIG. 8F  may provide for reduced costs, reduced environmental impact and/or passive orientation. In some embodiments, however, a three point mooring may be used as depicted in  FIG. 8A . In various such embodiments, directional controls may be attached to the WEC  100  and mooring to rotate the WEC into the oncoming waves. 
         [0072]      FIGS. 8B-E  depict different attachment positions  804  to the forward region of the HCS  116 . In some embodiments illustrated by  FIG. 8B , a single horizontal mooring line  802  attaches to the center of the HCS  116 . In the other configurations illustrated in  FIGS. 8C-E , two horizontal mooring lines  802  are attached to the HCS  116  at progressively wider spacing. This spacing of the horizontal mooring line(s)  802  allows for varied degrees of yaw stability of the WEC  100  at the mooring attachment. Furthermore, any mooring line  802 ,  808  and/or any number of mooring lines  802 ,  808  may be joined at any location on the WEC  100 . In various power generation embodiments, the WEC  100  may also be connected to an electrical output destination  812  via an electrical line  810 . Electrical line  810  may be supported to follow any underwater path and is not limited to the “lazy s-curve” configuration shown in  FIGS. 8A and 8F . Electrical output destinations  812  may include, but are not limited to, utility grids, transformers, batteries, devices, equipment, or vessels that consume electrical power, etc. 
         [0073]    In various embodiments wherein uninhibited 360-degree rotation of one or more floats  902 ,  904  is possible, one or more floats  902 ,  904  may become overtopped as shown in  FIG. 9A , such that the overtopped float (e.g.,  904  as shown) is capsized and aft of the nacelle  906 . Most commonly this will result from a force exerted by a large wave. The floats  902 ,  904  are safe, and operational, in this position; however, such floats  902 ,  904  may not be producing optimum power. When operationally appropriate, it may be preferred that some method be in place to return the float to the forward position. 
         [0074]    In various embodiments, illustrated in  FIGS. 9A-F , the overtopped float  904  may be dynamically ballasted such that it becomes negatively buoyant and sinks to a lower vertical orientation as depicted in  FIGS. 9B-C . From this position, the overtopped float  904  may be de-ballasted such that a ballast chamber at the top of the overtopped float  904  is buoyant, thereby creating a moment to rotate the float in the forward direction as depicted in  FIG. 9D . The overtopped float  904  may then rise into proper position at the surface as depicted in  FIGS. 9E-F . In other embodiments, the ballasting sequence described above may be implemented, but the float motion is supplemented with a controlled application of generator damping. In such a damping control mode, damping (torque) may be applied to the first PTO when rotating in the aft direction and damping (no torque) may not be applied when rotating in the forward direction. This damping control mode acts similar to a ratchet mechanism, or soft ratchet, promoting motion of an overtopped float toward the correct orientation. 
         [0075]    In further embodiments, the ballasting sequence described above may be implemented, but the float motion is supplemented with a controlled application of motor operation. In such motorized control modes, the first PTO may be driven as a motor to drive the overtopped float into the correct orientation. In still further embodiments, the overtopped float is completely de-ballasted and the float motion is supplemented with a controlled application of motor operation to drive the first float back over the top of the nacelle  906  to drive the overtopped float into the correct orientation. In yet still further embodiments, requirements may exist to prevent uninhibited 360-degree float  902 ,  904  rotation. Examples of such embodiments may include special operational or deployment scenarios that do not allow float overtopping. In systems with this need, end stops or limit straps may be used to constrain float motion. 
         [0076]    In many embodiments in accordance with the present disclosure, the spars  104 ,  106  have a deep draft and are too deep for vertical orientation when towed into or out of port. One skilled in the art will recognize in view of this disclosure that certain positioning of the floats  108 ,  110 , nacelle  102 , and spars  104 ,  106  relative to the ocean surface will have beneficial results for certain modes of transport and operation. For example, in some embodiments the WEC  100  may need to be towed to or from its operational location for deployment or recovery in an orientation different from its nominal operating position. The position that allows for the least drag may also reduce unnecessary forces on the operable components (e.g., floats  108 ,  110 , spars  104 ,  106 , nacelle  102 , etc.) during transport. Reorientation of a float  108 ,  110  and/or a spar  104 ,  106  may occur due to changes in ballast or operational conditions. To improve the ability to transit the WEC  100  into and out of port, the lower regions of the spars  104 ,  106  and a HCS  116  may be designed to be de-ballasted or attached with lift bags to raise the low region to the surface. In this position, the floats  108 ,  110  may be positioned between the nacelle  102  and HCS  116  as depicted in  FIGS. 10A-B . In this case, maximum component deballasting will allow for the WEC  100  to minimize its draft and maximize the navigable waterways through which it can move in tow without hitting bottom. 
         [0077]    Likewise, in embodiments requiring advance preparation for survival mode or extreme waves or weather, it will be apparent in view of this disclosure that, by PTO control, ballast control, locking mechanism, braking mechanism, ratchet mechanism or any combination of these approaches, a float may be lowered below the water surface. In some such embodiments, the first float  108  is reoriented to a nested floating position as depicted in  FIGS. 10A-B  with the nacelle  102  serving to shadow the weather, providing protection and increasing survivability. In various embodiments the first float  108  may still be operational in this nested position and able to capture energy. In further embodiments, as depicted in  FIG. 10D , a float is ballasted to be lower in the water and less exposed to severe weather or other conditions. In the most extreme weather conditions, when all measures are necessary to assure survivability, the first float  108  and second float  110  may be ballasted with water to submerge both into a vertical orientation as depicted in  FIG. 10C . In still further embodiments, environmental conditions may dictate that a float  108 ,  110  rotate to a position in which it is nested with another float. The float  108 ,  110  can be returned to its nominal position by PTO control, ballast control, locking mechanism, braking mechanism, ratchet mechanism or any combination of these approaches. 
       EXEMPLIFICATION 
       [0078]    WECs  100  and their constituent components (e.g., floats  108 ,  110 , spars  104 ,  106 , nacelles  102 , HCSs  116 , etc.) made in accordance with the present disclosure may be configured with any size, shape, relative position, or combination thereof. However, in many embodiments it may be preferred to optimize WEC  100  design (e.g. varying sizes, positions, and geometries of floats  108 ,  110 , spars  104 ,  106 , nacelles  102 , HCSs  116 , etc.) to maximize energy output relative to cost (e.g., minimize a cost of energy (COE)). Each WEC  100  design may be optimized in view of mission parameters (e.g., pumping, powering a data buoy, powering a surveillance sonobuoy, powering an oil platform, providing utility-scale electricity to a grid, etc.) and one or more wave climate conditions in which the WEC  100  may be deployed.  FIGS. 11-15C  depict the details of four exemplary configurations of WECs  100  optimized for various mission/climate inputs. 
         [0079]    Referring now to  FIGS. 11 ,  12 A-C,  13 A-C,  14 A-C, and  15 A-C, the exemplary WECs  100  shown may be used for a range of applications. The smallest illustrated example  1102  is a 10 Watt, 500 pound displacement system having a fully deployed length of 1.44 meters and a fully deployed depth of 1.75 meters. Such systems may, in some embodiments, drive low volume pumps and/or deliver electricity to low power sensors (e.g., wave instruments, temperature sensors, salinity sensors, wind sensors/anemometers, RF or satellite communications, etc.). Additional specifications of a WEC  100  in accordance with this exemplary embodiment are provided in  FIGS. 12A-C . 
         [0080]    The second illustrated example  1104  is a 1,500-5,000 Watt, 10,000-40,000 pound displacement system having a fully deployed length of 5 meters and a fully deployed depth of 6.07 meters. Such systems may, in some embodiments, drive somewhat higher volume pumps (e.g., water or oil) than a 500 pound displacement system  1102  and/or deliver electricity to various devices (e.g., unmanned underwater vehicle charging, autonomous vehicle charging, autonomous underwater vehicle charging), sensors as described above, or and/or various vessels/platforms (e.g., oil platforms). Additional specifications of a WEC  100  in accordance with this exemplary embodiment are provided in  FIGS. 13A-C . 
         [0081]    The third illustrated example  1106  is a 200 kW, 1,400 ton displacement system having a fully deployed length of 23.03 meters and a fully deployed depth of 27.94 meters. Such a system may, in many embodiments, be used for utility-scale electric-grid or other offshore energy applications in moderate-activity wave fields. Additional specifications of a WEC  100  in accordance with this exemplary embodiment are provided in  FIGS. 14A-C . 
         [0082]    The largest illustrated example  1108  is a 400 kW-1 MW or more, 3,000 ton displacement system having a fully deployed length of 31.09 meters and a fully deployed depth of 37.72 meters. Such a system may, in many embodiments, may be used for utility-scale electric-grid applications in high-activity wave fields. Additional specifications of a WEC  100  in accordance with this exemplary embodiment are provided in  FIGS. 15A-C . 
         [0083]    Based on considered mission requirements and worldwide wave field characteristics, geometric dimensions ranging from 1 m to 36 m in fully deployed length and from 1.5 m to 45 m in fully deployed depth may be appropriate. However, it will be apparent that WECs  100  in accordance with the present disclosure may be larger or smaller depending on variations in the circumstantial inputs described above. 
         [0084]    It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to various exemplary embodiments, it is understood that the words which have been used herein, are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. 
       Method 
       [0085]    In another aspect the present disclosure includes methods for generating power using a WEC  100 .  FIG. 16  illustrates a method for generating power in accordance with various embodiments of the present disclosure comprising the steps of providing a wave energy converter (WEC) comprising a buoyant nacelle, a first spar, a second spar, a first float and a second float  1602  and deploying the WEC in a wave field  1604 . 
         [0086]    Providing a WEC comprising a buoyant nacelle, a first spar, a second spar, a first float, and a second float  1602  with various embodiments may include providing any WEC designed in accordance with the concepts and embodiments described above with reference to  FIGS. 1-15 . Deploying the WEC in a wave field  1604  may include deploying the wave energy converter in, for example, any body of water (e.g., ocean, sea, bay, river, lake, wave pool, etc.) of suitable width, length, and depth to accommodate the WEC. 
         [0087]    In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, one skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. For example, each feature of one embodiment can be mixed and matched with other features shown in other embodiments. Features and processes known to those of ordinary skill may similarly be incorporated as desired. Additionally and obviously, features may be added or subtracted as desired. The scope of the invention is thus indicated by the appended claims, rather than by the foregoing description and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.