Abstract:
Systems for wave energy conversion that have components that can survive the harsh marine environment and that can be attached to fixed structures, such as a pier, and having the ability to naturally adjust for tidal height and methods for their use are presented.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national stage application under 35 U.S.C. 371 of co-pending International Application No. PCT/US13/42597 filed on May 24, 2013 and entitled SYSTEMS AND METHODS FOR WAVE ENERGY CONVERSION, which in turn claims priority to U.S. Provisional Patent Application No. 61/651,814 filed on May 25, 2012, which is incorporated by reference herein in its entirety for all purposes. 
    
    
     STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     A portion of this invention was made under U.S. Department of Energy Grant No. ST#106801. The government may have certain rights in the invention. 
    
    
     BACKGROUND 
     This invention relates generally to methods and systems for capturing the energy of fluid waves in a basin, such as, for example, ocean waves. 
     A variety of technologies have been proposed to capture energy from ocean waves; however, each is in too early a stage of development to predict which technology would be most prevalent to future commercialization. Wave energy conversion technology exists today primarily in the research and development stage, and the state of the technology is commonly considered to be one to two decades behind the development of wind energy. Although wave energy research has been ongoing for the past several decades, primarily in the United Kingdom, wave energy research has lagged significantly behind wind energy due to funding and other political constraints. At the present time, there are no commercially operating wave energy facilities in the world, with the exception of the Pelamis wave energy converter (WEC), which has had limited commercial scale implementation off the coast of Portugal. 
     There are many approaches to wave energy conversion currently being tested in research facilities around the world. In general, these can be separated into several broad classes of devices: 
     Oscillating Water Columns—these devices utilize an enclosed box with its bottom open to the ocean. Water entering the box associated with the crest of the wave pushes air out through a small conduit, which is used to drive a turbine producing electricity. As the wave recedes, air is drawn into the box through the same (or a separate) conduit, again driving a turbine to produce electricity. 
     Overtopping Devices—these devices allow incoming waves to break over the top edge of the device leaving water trapped in a small reservoir. As the water drains, it turns a turbine, creating electricity. 
     Point Absorbers—these are moored devices, or buoys, that move up and down on the water surface. There are several methods of converting the up and down motion of the point absorber to electricity. One commonly used approach is the linear generator/buoy configuration, which uses an electric coil that surrounds a metal rod connected to a permanent magnet linear generator. This type of device is often configured on a buoy that floats out in the open ocean, but can also be configured with part of the device attached to a fixed platform. The devices described hereinbelow are point absorber technologies, with a novel method for converting the up and down motion of the buoy to electricity, as described below. 
     Oscillating Wave Surge Converters—these can be thought of us submerged flappers that move back and forth as a wave passes. This flapping motion is then converted to electricity through a variety of methods. Sometimes the motion is used to pump seawater to shore where the electrical generating process takes place. 
     Submerged Pressure Differential Devices—similar to the surge converters, these devices use pressure differences on the seafloor as a wave passes to pump seawater which can then be used to drive a turbine. 
     Attenuators—these devices float at the surface with a number of joints. As the device flexes due to surface wave action, pistons within the joints drive high pressure oil through hydraulic motors which then drive turbines to produce electricity. The Pelamis system, operating off the coast of Portugal, is an example of attenuator technology. 
     There is a need for systems for wave energy conversion that have components that can survive the harsh marine environment. There is also a need for systems that can be deployed off fixed structures such as a pier and have the ability to naturally adjust for tidal height. 
     BRIEF SUMMARY 
     Systems for wave energy conversion that have components that can survive the harsh marine environment and that can be attached to fixed structures, such as a pier, and have the ability to naturally adjust for tidal height and methods for their use are presented hereinbelow. 
     In one or more embodiments, the system of these teachings includes a structure, the structure being substantially stationary in response to wave motion in a wave medium, where the structure includes a rotating component in a linear to rotary convertor, the rotating component being operatively connected to an electricity generating component, a linear motion component operatively connected to the rotating component and configured such that motion of the linear motion component results in or from rotation of the rotating component and a first force field generating component operatively connected to the linear motion component. In those embodiments, the system also includes a float member at least partially surrounding a portion of the structure, the float member moving substantially vertically in response to a wave moving through the wave medium wherein the float member includes a second force field generating component, the first force field generating component and the second force field generating component configured to substantially prevent rotation of the linear motion component and to hold the linear motion component substantially stationary with respect to the float member; rotation of the rotating component results from the motion induced by motion of the float member. 
     In one or more instances, the system of these teachings includes a structure, the structure being substantially stationary in response to wave motion in a wave medium where the structure includes a lead screw configured to be rotatable, the lead screw being operatively connected to an electricity generating component, a lead nut disposed on the lead screw and configured such that motion of the lead nut results in or from rotation of the lead screw and a first force field generating component operatively connected to the lead nut. In those embodiments, the system also includes a float member at least partially surrounding a portion of the structure, the float member moving substantially vertically in response to a wave moving through the wave medium wherein the float member includes a second force field generating component, the first force field generating component and the second force field generating component configured to substantially prevent rotation of the lead nut and to hold the lead nut substantially stationary with respect to the float member; the lead screw being disposed substantially in a vertical direction defined by motion of the float member in response to the wave moving through the wave medium. 
     In one or more embodiments, the method of these teachings includes providing a wave energy conversion apparatus including a structure, the structure being substantially stationary in response to wave motion in a wave medium wherein the structure includes a rotating component in a linear to rotary converter, the rotating component being operatively connected to an electricity generating component and a linear motion component in the linear to rotary converter, and a float member at least partially surrounding a portion of the structure, the float member moving substantially vertically in response to a wave moving through the wave medium. In those embodiments, the method also includes holding the linear motion component substantially stationary with respect to the float member, whereby vertical motion of the float member causes the rotating component to rotate and drive the electricity generating component, thereby converting wave energy into electrical energy. 
     In one or more embodiments, the method of these teachings includes providing a wave energy conversion apparatus including a structure, the structure being substantially stationary in response to wave motion in a wave medium wherein the structure includes a lead screw configured to be rotatable, the lead screw being operatively connected to an electricity generating component and a lead nut disposed on the lead screw and configured such that motion of the lead nut results in/from rotation of the lead screw, and a float member at least partially surrounding a portion of the structure, the float member moving substantially vertically in response to a wave moving through the wave medium, the lead screw being disposed substantially in a vertical direction defined by motion of the float member in response to the wave moving through the wave medium. In those embodiments, the method also includes preventing rotation of the lead nut and holding the lead nut substantially stationary with respect to the float member, whereby vertical motion of the float member causes the lead screw to rotate and drive the electricity generating component, thereby converting wave energy into electrical energy. 
     For a better understanding of the present teachings, together with other and further objects thereof reference is made to the accompanying drawings and detailed description and its scope will be pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a graphical representation of a wave energy converter according to one embodiment of these teachings; 
         FIGS. 2 a  and 2 b    illustrate components of one embodiment of the wave energy converter of these teachings; 
         FIG. 3  illustrates other components of one embodiment of the wave energy converter of these teachings; 
         FIGS. 4 a  and 4 b    illustrate force field components in one embodiment of the wave energy converter of these teachings; 
         FIGS. 5 a -5 c    illustrate the operation of one embodiment of the wave energy converter of these teachings; 
         FIG. 6  illustrates another embodiment of the system of these teachings; 
         FIGS. 7 a , 7 b , 7 c    provide three examples of other linear to rotary converters that are within the scope of these teachings; 
         FIG. 8  shows another embodiment of the system of these teachings; and 
         FIG. 9  shows a further component of one embodiment of the wave energy converter of these teachings. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description presents the currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the claims. 
     “Lead screw,” as used herein, is a mechanical linear actuator that translates rotational motion to linear motion and includes both ball screws and lead screws. 
     “Lead nut,” as used herein, is a component in a linear actuator where rotational motion is converted to linear motion or vice versa and includes the nut in a lead screw, the ball assembly in a ball screw and roller assembly in a roller screw. 
     In one or more embodiments, the system of these teachings includes a structure, the structure being substantially stationary in response to wave motion in a wave medium, where the structure includes a rotating component in a linear to rotary convertor, the rotating component being operatively connected to an electricity generating component, a linear motion component operatively connected to the rotating component and configured such that motion of the linear motion component results in or from rotation of the rotating component and a first force field generating component operatively connected to the linear motion component. In those embodiments, the system also includes a float member at least partially surrounding a portion of the structure, the float member moving substantially vertically in response to a wave moving through the wave medium wherein the float member includes a second force field generating component, the first force field generating component and the second force field generating component configured to substantially prevent rotation of the linear motion component and to hold the linear motion component substantially stationary with respect to the float member; rotation of the rotating component results from the motion induced by motion of the float member. 
     One embodiment of a linear to rotating component is a lead nut/lead screw configuration. 
     In that embodiment, the system of these teachings includes a structure, the structure being substantially stationary in response to wave motion in a wave medium where the structure includes a lead screw configured to be rotatable, the lead screw being operatively connected to an electricity generating component, a lead nut disposed on the lead screw and configured such that motion of the lead nut results in or from rotation of the lead screw and a first force field generating component operatively connected to the lead nut. In that embodiment, the system also includes a float member (buoy) at least partially surrounding a portion of the structure, the portion of the structure including the lead screw and lead nut, the float member moving substantially vertically in response to a wave moving through the wave medium wherein the float member includes a second force field generating component, the first force field generating component and the second force field generating component configured to substantially prevent rotation of the lead nut and to hold the lead nut substantially stationary with respect to the float member; the lead screw being disposed substantially in a vertical direction defined by motion of the float member in response to the wave moving through the wave medium. 
     In one instance, the force field generating components are magnetic field generating components. 
     In one embodiment, the float member (buoy) surrounds an inner vertical shaft in the structure. The inner vertical shaft encases a lead screw that translates vertical motion of a lead nut into rotational motion. The lead screw is operatively connected to a bearing at one end and operatively connected to an electricity generating component (such as, for example, an alternator/generator) at the other end. Connection to the electricity generating component may be made by a variety of mechanisms (for example, but not a limitation of these teachings, the mechanisms can include a clutch in order to provide unidirectional rotation to the alternator/generator). Actuation of the lead nut is achieved by introducing a force field (a magnetic field in one instance) that forces the lead nut to move substantially in unison with the buoy. Motion of the lead nut results in rotation of the lead screw, which translates into generation of electricity. 
     In one instance, the force field components include a number of magnets (in one embodiment, neodymium magnets) of predetermined strength. A group of magnets is located in the buoy with one pole facing towards the lead nut and another group of magnets is mounted on the lead nut with poles located so as to result in a magnetic field forcing the lead nut to move substantially in unison with the buoy and preventing the lead nut from rotating. In other embodiments, additional magnets can be placed above and/or below the group of magnets at the buoy and/or lead nut, where the additional magnets further restrain motion of the lead nut. 
     In one instance, the buoy is designed so that it responds efficiently to changes in the water surface due to wave action, by matching the buoyant force provided by the submerged portion of the buoy to the weight of the buoy and the resistive three of the generator under various configurations. In another instance, the buoy is designed in order to optimize the motion of the body in order to optimize energy extraction (for example, moving in resonance with the dominant wave frequency). 
     An exemplary embodiment is shown below.  FIG. 1  is a graphical representation of a wave energy converter according to the exemplary embodiment. Referring to  FIG. 1 , the stationary structure includes a top mounting member  1024 , a bottom mounting member  1022 , a bottom mounting section  1018 , secondary mounting rods (or tubing)  1026  and a vertical shaft  1006 , with a lead screw  1004  located in the vertical shaft  1006 . The lead screw  1004  is operatively connected to an alternator/generator  1010 , which is mounted on structure  1020 , by means of a coupling mechanism  1012  and supported by structure  1016 . A buoy  1002  surrounds the vertical shaft  1006  and two secondary support rods  1008 . The mounting mechanism is omitted in  FIGS. 2A and 2B , in order to show the free-floating buoy  1202  and a lead screw  1204  enclosed by the center tubular structure and which is supported by a bearing at the bottom and coupled to a generator/alternator (a rotor)  1210  by means of a coupling mechanism  1212  at the top.  FIG. 2B  illustrates vertical shafts  1206 ,  1222 , support rods  1208 , support structures  1216 ,  1218 ,  1220 , and the bracket  1014 ,  1214  which has been incorporated into the design to allow for an array of permanent magnets to be secured to the inside of the buoy  1202 . A ferromagnetic material such as iron or steel may be used to intensify the magnetic field of the array. 
       FIG. 3  illustrates, for the exemplary embodiment, the second array of permanent magnets  1412  secured onto another bracket  1408  which is fastened to the lead nut. Also shown are a lead screw  1404 , the inner surface  1406  of the buoy  1402  and the permanent magnet array  1410  mounted on the inner surface  1406  of the buoy  1402 . The two concentric permanent magnet arrays  1410 ,  1412  create an attraction force extending from the buoy  1402  to the lead nut in several directions.  FIG. 4A  is a top-sectional view of the magnetic system in the buoy  1602  and on the lead nut. Each array is made up of magnets  1608 ,  1610  which alternate in direction in order to prevent the lead nut from spinning with respect to the buoy  1602 . The result of alternating poles is that a magnet  1610  on the lead nut experiences a force from adjacent magnets  1608  on the buoy  1602 , forcing the lead nut in place and preventing it from spinning.  FIG. 4B  illustrates the fields of attraction between the two substantially concentric arrays of permanent magnets  1608 ,  1610  with the use of ferromagnetic cores  1606 ,  1604  on the buoy  1602  and lead nut. 
     It should be noted that these teachings are not limited only to the exemplary embodiment. 
     Another embodiment of the system of these features is shown in  FIG. 6 . In the embodiment shown in  FIG. 6 , the buoy is constrained by a second shaft offset from the center but exterior to the buoy in order to prevent rotation of the buoy. 
     Other embodiments of the linear to rotary converter are shown in  FIGS. 7 a  and 7 b   .  FIG. 7 a    shows a rack and pinion linear to rotary converter and  FIG. 7 b    shows a lever system. In the embodiment shown in  FIG. 7 b   , a stationary (non-rotating) screw is located in the center of the tube; the nut provides the rotation, also rotating an outer housing, which is connected to a generator at the top of the screw. 
     In the embodiment shown in  FIG. 7B , a sealed tube  2010  encompasses an alternator  2014  and actuator  2016 ,  2018 ,  2020 , and the sealed tube  2010  contained within a vertical hollow structure (“shaft”)  2004  along which it may slide. A system of magnets  2012  couple the buoy  2002  and the sealed tube such that vertical motion of the buoy results in equal vertical motion of the tube. A set of fixed vertical rods  2006  act as a vertical guide for the buoy. A flanged casing (“sheath”)  2008  around each rod extends through the buoy. The sheath&#39;s position on the rod is maintained by friction or an alternative locking mechanism. The force of the buoy bumping against it will cause it to move only the distance it is pushed. The set of fixed sheaths provide a set of fulcrums  2032  for a set of internal levers  2030  which are magnetically coupled  2028  to the ball nut  2018  inside the sealed tube. To reinforce synchronous movement of all levers, the sheaths&#39; flanges may be connected to form one entity. 
     The actuator inside the sealed tube is comprised of a ball screw  2016  whose nut  2018  is supported by a linear guide  2020  mounted on a bearing  2034 . The bottom end of the screw is fixed  2022  and the free end of the screw is stabilized by a pair of repelling ring magnets  2024  (or repelling magnet structures) mounted on the outside of the ball screw and the inside of the linear guide. Linear movement of the levers about their fulcrum is translated through the magnetic coupling to the nut, which is forced to spin about the fixed screw, which, in turn forces the linear guide to rotate. 
     A shaft  2026  is connected to the rotating component, which drives a conventional alternator to generate electricity. Electricity generated by the alternator is conducted via a coiled cable to the end cap of the shaft. 
     In another embodiment, the linear to rotary converter is a piston pump driving fluid (air, water, hydraulic fluid), in a closed loop or open cycle, that then drives a turbine (see for example, http://www.pumpscout.com/articles-expert-advice/understanding-positive-displacement-pumps-aid89.html). 
     Another embodiment in which a stationary (non-rotating) screw is located in the center of the tube is shown in  FIG. 7 c   ; the nut provides the rotation, also rotating an outer housing, which is connected to a generator at the top of the screw. In the embodiment shown therein, the fixed screw is in the middle, and a threaded cap structure sits on top of it and rotates. The cap cannot be directly coupled to the buoy or there would be rotation problems, so the alternator (which would move up and down with the cap) is coupled to the buoy, and a reverse magnetic coupling is located at the bottom of the cap, which is then coupled to the buoy. The reverse magnetic coupling on the bottom allows force to be applied but both sides of the coupling don&#39;t have to rotate. 
     In the embodiment shown in  FIG. 7C , a fixed screw  2212  is aligned with a vertical direction of the hollow structure (“shaft”)  2214 . A threaded cap  2208  is mated with the screw and turns as it rises and falls due to force provided from the bottom through a common polarity magnetic coupling system  2210 , and from the top through bearings associated with connection between the shaft of the screw cap  2216  and an alternator  2202 . The alternator cage  2218  and the bottom forcing plate  2220  are linked by a magnetic coupling system  2204  to a buoy  2206 , which enables the transfer of buoy motion to the components inside the shaft  2214 . The alternator cage is prevented from spinning by tabs on the cage that align with grooves on the inside surface of the shaft  2214 . Electricity generated by the alternator  2202  is conducted via a coiled cable to the end cap of the shaft. Alternatively, electric current can be carried to the end cap through conducting channels within the grooves on the inside surface of the shaft  2214   
     In yet another embodiment, shown in  FIG. 8 , the main tube has threads on the inside (in one instance, the threads are molded into the PVC or, in another instance, there is a non-magnetic insert, for example, aluminum or stainless steel insert). A disk in the middle spins in the threads when force is applied up or down. The generator is attached to this disk and travels up and down the tube with the buoy, but is kept from spinning by several grooves cut through the threads into the side of the tube. In one instance, there is a reverse magnetic coupling at the bottom (allowing one side to spin while the other does not), and a direct magnetic coupling to the buoy at the top (the generator, which is not spinning). 
     An alternative embodiment is shown in  FIG. 8 . In this embodiment, vertical motion of the buoy  2402  is transferred to the inside of the shaft  2420  through a magnetic coupling system  2404 . Inside the shaft force is applied specifically to a bottom force plate  2408  and an alternator cage  2416 . The bottom force plate is connected to a rotating component  2412  by a common polarity magnetic coupling system  2410  allowing the rotating component  2412  freedom to rotate. The rotating component  2412  is designed with threads on its outer circumference that mate with threads  2406  on the interior surface of the shaft  2420 . The threads on the circumference of the rotating component may incorporate ball bearings or other mechanisms to reduce rotational friction. A shaft  2414  is connected to the rotating component, which drives a conventional alternator  2416  to generate electricity. The alternator cage is prevented from rotating by tabs on the cage that align with grooves on the inside surface of the shaft  2214 . Electricity generated by the alternator  2416  is conducted via a coiled cable  2418  to the end cap of the shaft. Alternatively, electric current can be carried to the end cap through conducting channels within the grooves on the inside surface of the shaft  2420 . 
     In a number of the embodiments disclosed hereinabove, the components are separated from each other and operatively coupled.  FIG. 9  shows an embodiment of a structure that holds the components separated from each other and couples the two components such that displacement of one component results in displacement of the other component. Referring to  FIG. 9 , in the embodiment shown therein, a first group of permanent magnet elements  2206  is disposed on a surface of one component  2220  and a second group of permanent magnet elements  2212  is disposed on a surface of another component  2208 . Like poles of the of the first group of permanent magnets elements  2206  and of the second group of permanent magnet elements  2212  are opposite each other, thereby keeping the two components separated but coupled since displacement of one component towards the other component will cause displacement of the other component. 
     In one or more embodiments, the method of these teachings includes disposing a float member in the wave medium, a float member being configured to move substantially vertically in response to a wave moving the wave medium; the float member at least partially surrounding a portion of a structure, the structure being substantially stationary in response to wave motion in a wave medium, the structure including a rotating component in a linear to rotary converter (L-R converter), the rotating component being operatively connected to an electricity generating component, a linear motion component in the L-R converter, the linear motion components operatively connected to the rotating component; motion of the linear motion component results in or from rotation of the rotating component; and a first force field generating component operatively connected to the linear motion component, the float member including a second force field generating component, configuring the first force field generating component and the second force field generating component to hold the linear motion component substantially stationary with respect to the float member, and generating electrical energy by rotation of the rotating component driving the electricity generating component. 
     In one or more other embodiments, the method of these teachings includes providing a wave energy conversion apparatus including a structure, the structure being substantially stationary in response to wave motion in a wave medium wherein the structure includes a rotating component in a linear to rotary converter, the rotating component being operatively connected to an electricity generating component and a linear motion component in the linear to rotary converter, and a float member at least partially surrounding a portion of the structure, the float member moving substantially vertically in response to a wave moving through the wave medium. In those embodiments, the method also includes holding the linear motion component substantially stationary with respect to the float member, whereby vertical motion of the float member causes the rotating component to rotate and drive the electricity generating component, thereby converting wave energy into electrical energy. 
     In the embodiments in which the linear to rotary converter is a lead nut/lead screw configuration, the method of these teachings includes providing a wave energy conversion apparatus including a structure, the structure being substantially stationary in response to wave motion in a wave medium wherein the structure includes a lead screw configured to be rotatable, the lead screw being operatively connected to an electricity generating component and a lead nut disposed on the lead screw and configured such that motion of the lead nut results in/from rotation of the lead screw, and a float member at least partially surrounding the structure, the float member moving substantially vertically in response to a wave moving through the wave medium, the lead screw being disposed substantially in a vertical direction defined by motion of the float member in response to the wave moving through the wave medium. In those embodiments, the method also includes preventing rotation of the lead nut and holding the lead nut substantially stationary with respect to the float member, whereby vertical motion of the float member causes the lead screw to rotate and drive the electricity generating component, thereby converting wave energy into electrical energy. 
       FIGS. 5A-5C  illustrates the method of these teachings by illustrating the operation of the exemplary embodiment.  FIG. 5A  shows the magnets  1816  mounted on bracket  1804 , which is located on the buoy  1802 , the magnets  1814  mounted on bracket  1810 , which is fastened to the lead nut  1808 , and the buoy  1802  in the rest position, i.e. no waves.  FIG. 5B  illustrates wave forces pushing up on the buoy  1802  with arrows on the bottom of the buoy  1802 . The magnetic fields, from the magnets  1814 ,  1816  that prevent the lead nut  1808  from spinning also pull the lead nut  1808  upward with the buoy  1802 , which forces the lead screw  1812  to spin.  FIG. 5C  illustrates gravity pulling the buoy  1802  back down with arrows at the bottom of the buoy  1802 . Again, the lead nut  1808  is pulled along by the magnetic fields and, in one embodiment, forces the lead screw  1812  to spin, in the opposite direction. Other embodiments can include mechanisms to then disengage the lead nut  1808  in order to obtain unidirectional rotation of the lead screw  1812  (see, for example, U.S. Pat. No. 3,757,591, incorporated by reference herein in its entirety and for all purposes). 
     For the purposes of describing and defining the present teachings, it is noted that the term “substantially” is utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The term “substantially” is also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     Although the invention has been described with respect to various embodiments, it should be realized these teachings are also capable of a wide variety of further and other embodiments within the spirit and scope of the appended claims.