Abstract:
An energy harvester capable of providing motion from fluid flow includes a Magnus cylinder defined by a cylinder driven by a motor causing the cylinder to rotate so that lift is created by the fluid flowing past the cylinder. A channel or system may be provided to direct the fluid flow to the cylinder. The rotating cylinder configuration is integrated into a mechanical device that is designed to transfer the lift into a rotary mechanical motion to drive a generator. The device can be utilized in either air or hydraulic environments. A modification of the energy harvester can be configured to utilize the electricity generate to produce hydrogen for use in fuel cells or for combustion.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/206,044 filed Jan. 26, 2009, contents of the foregoing application being incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to a device for harvesting energy and more specifically to an energy harvester that extracts energy from fluid flow by exploiting the lift created by the flow as it passes a rotating cylinder. The device can be used with hydro-pneumatic, hydro, wind, or wave power systems. 
       BACKGROUND 
       [0003]    Hydropower systems are used for generating power from the tidal or current motion of water in oceans, bays, and rivers. Typically, such systems employ a high water head and high water flow conditions. System operating parameters that include both a high water head and high flow conditions limit the suitable sites for locating fluid flow energy harvesters. Conventional hydro turbine technology, which involves positioning a powerhouse in a dam body with turbines located below the lowest water level, has been applied at mountain river and waterfall sites where a large water head can be developed. Consequently, powerhouses using hydro turbines are generally installed in large and complicated dam structures capable of withstanding the enormous water pressures generated. On the other hand, the hydro energy potential of thousands of rivers, streams, and canals remain untapped because hydro turbines, as an economical and practical matter, do not operate effectively with a low water head, in other words, when water level differences are about three meters or less. Such conventional hydro turbines need significant water depth for installation and cost-efficient operation. 
         [0004]    Systems have also been developed to generate power using lower water head. These systems are described in U.S. Pat. Nos. 4,717,832, 5,074,710, and 5,222,833, the disclosures of which are incorporated herein by reference. 
         [0005]    Systems for utilizing tidal motion and current flow of oceans and rivers are also known. Such systems usually require a dam or other physical structure that separates one part of a water body from another part. A difference in water levels is thereby created which provides a pressure differential useful for driving mechanical devices such as hydro turbine generators. 
         [0006]    Also, axial-flow turbine type devices deriving power from liquid flow in tidal runs and streambeds are known. Such devices are disclosed in U.S. Pat. No. 3,980,894 to P. Vary et al., U.S. Pat. No. 3,986,787 to W. J. Mouton, Jr., U.S. Pat. No. 4,384,212 to J. M. Lapeyre, U.S. Pat. No. 4,412,417 to D. Dementhon, and U.S. Pat. No. 4,443,708 to J. M. Lapeyre. 
         [0007]    Pivotal flow-modifying means is shown in the above Mouton, Jr. patent in a multiple unit embodiment. 
         [0008]    U.S. Pat. No. 4,465,941 to E. M. Wilson discloses a water-wheel type device for the purpose of flow control pivotal valves or deflectors. 
         [0009]    Additionally, various Magnus effect generating systems have been envisioned. The Magnus effect was first publicized by Professor G. Magnus in 1853. The Magnus effect is a physical phenomenon in which a spinning object creates a current of rotating fluid about itself. As the current passes over the object, the separation of the turbulent boundary layer of flow is delayed on the side of the object that moves in the direction of the fluid flow and is advanced on the side of the object that moves counter to the direction of the fluid flow. Thus, pressure is exerted in the direction of the side of the object that moves in the same direction of the fluid flow to provide movement substantially perpendicular to the direction of fluid flow. Briefly stated, when a rotating cylinder encounters a fluid flow at an angle to its rotational axis, a lifting force (lift) is created perpendicular to the flow direction. If a rotating cylinder is mounted on a vertical axis, the lift is developed at right angles to the direction of water flowing past the cylinder, left or right depending upon the direction of rotation. 
         [0010]    The use of the Magnus effect can also be used to describe, among other things, the curved pitches of baseball and the shooting of airplane guns transversely to the airplane&#39;s path of travel. 
         [0011]    Various patents disclose the use of the Magnus effect for airplane lift, steering a boat, and for assisting in submarine steering. 
         [0012]    The Magnus effect is utilized in U.S. Pat. No. 4,446,379 to Borg et al., which discloses Magnus cylinders mounted for rotation at right angles to shafts that are revolved about a generally vertical axis. The shafts are free to rotate 180 degrees. The Magnus cylinders are continuously rotated in the same angular direction. At one position of revolution of the shafts, the cylinders rotate on an axis generally parallel to the axis of revolution of the shafts. When the apparatus is immersed in a fluid flow (gaseous or liquid) a torque of rotation is developed when the shafts are aligned with the fluid flow, and this torque of rotation is reduced as the shaft approaches a position transverse to the fluid flow. As the shafts pass this transverse position, a torque is developed by the rotating cylinder that rotates the shafts 180 degrees at which point the formerly downwardly depending cylinder is now upright and the formerly upright cylinder is now downwardly depending on its shaft. The device was designed to utilize two or more shafts to which cylinders are attached, and there is continuous production of torque about the axis of revolution of the shafts. The complexity of this device makes it a difficult device to build or operate. If the Magnus effect is to be used to generate power, a simpler device is needed. 
         [0013]    U.S. Pat. No. 4,582,013 to Holland describes a self-adjusting wind power machine that uses a cylinder. 
         [0014]    Co pending U.S. Patent application 20090058091 entitled “Magnus Force Fluid Energy Harvester,” the disclosure of which is incorporated by reference herein in its entirety, describes an energy harvester capable of providing motion from fluid flow. The energy harvester includes a Magnus cylinder defined by a cylinder driven by a motor causing the cylinder to rotate so that lift is created by the fluid flowing past the cylinder. A channel or system may be provided to direct the fluid flow to the cylinder. The rotating cylinder configuration is integrated into a mechanical device that is designed to transfer the lift into a mechanical motion to drive a generator. The mechanical motion due to the created lift is reversed by using a stalling mechanism and counter balanced mechanism. This creates a bi-directional motion that can be captured and used to drive a generator. The device can be utilized in either air or hydraulic environments. A modification of the energy harvester can be configured to utilize the electricity generated to produce hydrogen for use in fuel cells or for combustion. 
         [0015]    Pneumatically driven systems using turbine blades have also been developed. However, these systems normally use blades that rotate at high speeds. These rotating blades are problematic as any sizable foreign object encountered by the system can damage the blades, thereby compromising the structural integrity of the system. When the system utilizes the flow of air such as in the use of turbine blade aircraft, bird strikes can cause significant damage to the rotating blades, as can stones or other debris inadvertently or intentionally injected into the rotating blades. When the system is a water system, the injection of aquatic plants and animals as well as debris frequently found in waterways (e.g., chunks of wood) can also cause damage. 
         [0016]    The majority of the systems envisioned by the aforementioned technologies utilize rotating blades that are noisy, detrimental to both flora and fauna, and require dams that interfere with the motion of the flowing water. Additionally, the systems that are utilized in these applications significantly obstruct sunlight, thereby detrimentally affecting aquatic plant life. These approaches are normally resisted by the affected communities due to the harm caused to flora and fauna and the damming of the body of water that negatively affects community activities. Damming and rerouting water flow can also cause significant upstream destruction of wildlife habitats. 
         [0017]    Low head and low flow hydraulic conditions are prevalent throughout the world. The difficulty described therein is that there are no simple and easy methods to harness the energy from low head water sources to create power. 
         [0018]    However, despite the technological efforts described previously there is no known system capable of generating electricity from low head/high power and low power sources such as tidal and/or river flow and being capable of continuous generation under changing flow conditions. 
         [0019]    Given the increasing demand for industrial electricity in view of the issues related to the current state of the art of fluid flow energy harvesters, a need exists for a system that does not harm flora or fauna and can be introduced into the environment without interfering with the natural water flow or blocking the majority of the sunlight to the bottom of the body of water. A need also exists for an environmentally friendly, quiet, efficient, and simple energy harvester that can operate in low head and low flow conditions. 
       SUMMARY OF THE INVENTION 
       [0020]    As used herein, the term “hydro application” and “hydraulic” are used to describe the use of the energy harvesting device with regard to liquid, and the term “gas application” and “pneumatic” are used to describe the use of the energy harvesting device with regard to gas (e.g., air). 
         [0021]    As used herein, the term “lift” refers to a force that is perpendicular to a direction of fluid flow. 
         [0022]    As used herein, the term “electrical grid” refers to any system used to utilize or transport electrical current. 
         [0023]    The present invention provides an energy harvesting device (or energy harvester) capable of generating energy from low power hydraulic or pneumatic flows using lift generated by the Magnus effect by taking advantage of the availability of sources of fluid flowing under low head pressure and/or flows of velocities of 1 feet per second or greater. The energy harvester comprises inflow and outflow fluid channels, an energy harvester chamber, and a series of revolving cylinders, which is typically mounted in a radial configuration and transversely to the direction of fluid flow. The inflow channel is provided with diverters and baffles to direct the flow of fluid to the cylinders. 
         [0024]    The lift can be transferred into a mechanical system, for example, it can be transferred to a generator via a driveshaft or a similar mechanism. 
         [0025]    For gas applications, the energy harvester applications are under ultra low head pressure fluid flow, and the energy harvester can readily deliver significant lift causing the system to drive a conventional industrial generator. This allows the energy harvester of the present invention to achieve efficiencies higher than energy harvesters of the prior art. For hydro applications, the energy harvester applications are under ultra low head flow or any strong current of 1 foot per second or greater, which is less than needed for prior art energy harvesters. Because radial hydro cylinders or air cylinders are used in the present applications, a highly scaleable application is achieved due to the energy required to develop lift and the lift developed being very large and having the ability to be focused at the central shaft. 
         [0026]    In the case of pneumatic energy conversion, the channel forces the air to be directed at the air cylinder and delivers it so maximum lift is created. The energy captured in the flowing air is then converted to mechanical energy. Connection of the energy harvester to an electric generator allows for the generation of electrical energy. Increasing the speed of the air energy harvester to the generator&#39;s speed can be accomplished without additional gearing. 
         [0027]    In a hydro application embodiment, the energy harvester can be mounted in a self-floating configuration and is attached to a vessel or platform located in a current of 1 foot per second or greater, such as in a tidal channel. In such an embodiment, the energy harvester is located just below the surface of the water, where the current velocity is greatest, and is retained in that location by virtue of the rise and fall of the vessel with the water. The rotary energy harvester embodiment is uniquely suited for this application. A housing to channel the flow to the energy harvester may by provided if desired, but is not necessary if the current velocity is sufficiently great. The energy harvester is connected to a suitable electric generator, which may be mounted on the vessel in a water tight chamber or which may be remotely located. Since the energy harvester is located in the water, the lift is converted into mechanical energy to drive the generator. 
         [0028]    Alternatively the flow can be concentrated so that the speed of the fluid passing the air or hydraulic cylinders is accelerated to increase the lift of the cylinder. Channeling the flow from a larger cross section into a smaller cross section where the cylinder can take advantage of the increased flow speed of the fluid facilitates an increase in the lift of the cylinder. 
         [0029]    Methods herein utilize the air or hydraulic cylinders to produce a rotating motion to directly drive a rotating generator. This would use a series of cylinders arranged in a wheel format and either a single motor or a series of motors to drive the cylinders. The cylinders are longitudinally separated in pairs so that flow from the first or leading cylinder is accelerated and further accelerated by the second or next cylinder which is in the rear of the first cylinder and positioned at least 30 degrees out of phase but not more than 179 degrees out of phase of the first cylinder. This positioning allows the fluid to be accelerated down the longitudinal length of the machine and accelerated by each cylinder thereby increasing the torque created by the lift of each cylinder, the lift being used to drive the rotating generator. The present invention is not limited with regard to the number of cylinder pairs that can be installed, however, as any number of cylinder pairs can be installed to generate the desired torque. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0031]      FIG. 1  is a schematic side view representation of a radial device with staggered rotating Magnus cylinders in an axial position within a channel defined by walls; 
           [0032]      FIG. 2  is a schematic end view representation of a radial device with staggered rotating Magnus cylinders in an axial position within a channel defined by walls; 
           [0033]      FIG. 3  is a schematic top view representation of a radial device with staggered rotating Magnus cylinders in an axial position within a channel defined by walls; 
           [0034]      FIG. 4  is a schematic side representation of a radial device with staggered rotating Magnus cylinders in an axial position within a tube; 
           [0035]      FIG. 5  is a schematic end representation of a radial device with staggered rotating Magnus cylinders in an axial position within a tube; 
           [0036]      FIG. 6  is a schematic representation of a double concentric shaft used to drive the Magnus cylinders and transmit the power to the generator; 
           [0037]      FIG. 7  is a graphical representation of the torque vs. RPM for a flow of 2 feet per second for a machine schematically shown in  FIGS. 4 and 5 ; 
           [0038]      FIG. 8  is a graphical representation of the torque vs. RPM for a flow of 4 feet per second for a machine schematically shown in  FIGS. 4 and 5 ; 
           [0039]      FIG. 9  is a schematic representation of the Magnus cylinder force diagram;\ 
           [0040]      FIG. 10  is a schematic side representation of a radial device with planar rotating Magnus cylinders in an axial position within a tube; 
           [0041]      FIG. 11  is a schematic end representation of a radial device with planar rotating Magnus cylinders in an axial position within a tube; 
           [0042]      FIG. 12  is a schematic side representation of a radial device with double planar rotating Magnus cylinders in an axial position within a tube; 
           [0043]      FIG. 13  is a schematic end representation of a radial device with double planar rotating Magnus cylinders in an axial position within a tube; 
           [0044]      FIG. 14  is a schematic representation of a double concentric shaft used to drive the Magnus cylinders and transmit the power to the generator which then creates Hydrogen and oxygen; 
           [0045]      FIG. 15  is a schematic representation of an energy harvester of the invention floating on a barge structure; 
           [0046]      FIG. 16  is a schematic representation of an energy harvester of the invention attached to a bridge structure; 
           [0047]      FIG. 17  is a schematic representation of an energy harvester of the invention attached to the bottom of the fluid channel by a bridge structure; and 
           [0048]      FIG. 18  is a schematic representation of an energy harvester using a gear train and drive shaft system. 
           [0049]      FIG. 19  is a schematic representation of an energy harvester incorporating a pinion gear to drive a generator. 
           [0050]      FIG. 20  is a schematic representation of an energy harvester incorporating a pinion gear to drive a pump. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0051]    An energy harvester for use in fluid flows according to the present invention is shown in  FIGS. 1 ,  2  and  3  and is mounted to a structure where the energy harvester is in communication with a fluid flow  90 . The energy harvester comprises inflow fluid channel walls  4 ,  5 ,  6  and  7 , energy harvester channel side walls  8 ,  9 ,  10 , and  11  that receive a flow  90  from the fluid inflow channel walls  4 ,  5 ,  6  and  7 . A main shaft  40  is located within a channel  95  defined by the inflow fluid channel walls  4 ,  5 ,  6 , and  7  and the channel side walls  8 ,  9 ,  10 , and  11  in which the fluid flow  90  is received. Magnus cylinders  200 ,  201 ,  210 , and  211  are each mounted on a respective central axis  205  between the main shaft  40  and channel side walls  8 ,  9 ,  10  and  11 . The walls can also be replaced with a tube  307  as shown in  FIG. 4  and  FIG. 5 . The fluid flow path is defined by an inflow fluid channel formed by inflow fluid channel walls  4 ,  5 ,  6  and  7 , an outflow fluid channel formed by channel side walls  8 ,  9 ,  10  and  11 , and an energy harvester chamber  12  disposed between the inflow fluid channel and the outflow fluid channel and formed from channel side walls  8 ,  9 ,  10  and  11 . The walls can also be curved either in the side or bottom walls in this configuration and have opposite elevations in the plane parallel to the fluid flow path. This acts as a concentrator for the fluid flow by channeling a greater volume of fluid to the energy harvester thereby increasing the speed of the fluid that will increase the lift generated by the cylinder. This intensification can be used in any of the embodiments envisioned by the present invention. It is also seen in the data presented in  FIGS. 7 and 8 . This data shows a significant improvement in torque from the theoretical to the actual. This is due to the amplification of the lift as the fluid is accelerated as it passes the first Magnus cylinder  200  and then moves down the next Magnus cylinder  201  where it is accelerated again and then moves down the next Magnus cylinder  210  and where it is accelerated again and then moves down the next Magnus cylinder  211 . The Magnus force is developed as shown in  FIG. 9 . To increase the lift the energy harvester is replicated within 1-20 diameters of the Magnus cylinder. The fluid flow  90  can be hydraulic or pneumatic (air or gas). 
         [0052]    The cylinders are mounted inside a channel formed by a passage defined by the opposed channel side walls, an optional bottom chamber wall, the inflow fluid channel walls, and the outflow fluid channel walls. This passage directs the flow through the energy harvester. The cylinders are oriented transversely to the flow through the passage and are mounted for rotation, for example, via bearings  1080  and  1085  in cylinder supports  1000  and  1105  shown in  FIG. 6 . 
         [0053]    The cylinders are rotated by a drive mechanism as shown in  FIG. 6 . The lift is generated via the Magnus effect when the flow is concentrated through the channel  95  and past the cylinders  200 ,  201 ,  210  and  211 . The flow through the channel  95  and past the cylinders  200 ,  201 ,  210 , and  211  forces the mechanism to rotate the main shaft  40  mechanism causing the drive mechanism to rotate generator  1030 . This concentrating of fluid in the channel accelerates the flow by funneling the fluid towards the cylinders  200 ,  201 ,  210 , and  211 . However, the acceleration is unexpectedly amplified by the Magnus cylinders themselves and causes increased lift due to the acceleration of the fluid in the energy harvester chamber  12 , thereby increasing the lift. The flow is further accelerated by each cylinder to increase the lift for the successively-positioned cylinders in the flow path. The diameters of the cylinder  200 ,  201 ,  210 , and  211  may be the same, or they may vary relative to each other. 
         [0054]    Therefore the performance of the radial Magnus turbine is improved by staggering the Magnus cylinders along the central shaft so that the each cylinder is in a separate plane as shown in  FIGS. 1 ,  2 ,  3 ,  4 , and  5 . The fluid flow  90  can be hydraulic or pneumatic (air or gas). 
         [0055]      FIGS. 4 and 5  show a rotational system that uses the fluid flow in the channel to rotate the cylinders in perpendicular fashion to develop lift perpendicular to the flow. The energy harvester chamber is a pipe  307 . The design makes the device well suited for in-pipe operation. The round pipe shape further increases the torque created by the lift of the cylinders by keeping the fluid contained in a focused energy harvester chamber  12 . The increase in torque is due to the increase in speed of the water due to the acceleration of the water around the Magnus cylinder and then interacting with the Magnus cylinder in a positive manner thereby generating higher lift forces. To increase the lift, the energy harvester is replicated within 2-20 diameters of the Magnus cylinder in the down stream direction of the flow. The fluid flow  90  can be hydraulic or pneumatic (air or gas). 
         [0056]      FIG. 6  shows the double shaft that transmits torque to drive the Magnus cylinders, the rotations of which in turn drive the outer shaft to drive the generator. A motor  1005  is connected to pulley  1010 . A belt  1021  transmits torque from pulley  1010  to pulley  1020  to drive shaft  1045  supported in bearings  1085  and  1080 . Driving the shaft  1045  drives the central axes  1205  and  1215 , thereby causing Magnus cylinders  1200  and  1210  to rotate. This creates lift when subjected to flow  90  as shown in  FIGS. 4 and 5 . This lift then causes the outer shaft  1040  to rotate which drives the drive pulley  1015  to drive generator drive pulley  1031  (via belt  1032 ) to drive the generator  1030 . A pinion gear  1029  or bull gear  1028  may be used to drive the generator  1030  as shown in  FIG. 19 . Generator  1030  can be attached to battery  99  or to electrical grid  98 . The motor  1005  can be operable under electric, pneumatic, or hydraulic power and reversible to allow the rotation of the central shaft  40  to be the same direction if the flow  90  is reversed. The generator  1030  can be replaced with a pump  5000  as shown in  FIG. 20  to pump fluids such as air or water. The pump  5000  input for the fluid is  5010  and the output from the pump  5000  is  5020 . The fluid pumped can be a gas like air or a liquid like water. 
         [0057]    At least two sets of bevel gears  1050  and  1060  are located on shaft  1045  to drive the two Magnus cylinders (e.g., cylinder  1200  and cylinder  1210  attached to the central axes  1205  and  1215 ). Bevel gear  1055  is attached to shaft  1215  that is positioned to be in communication with bevel gear  1050  and bevel gear  1065  is attached to central axis  1205  which is positioned to be in communication with bevel gear  1060 . The rotary motion of the motor  1005  drives the rotation of the Magus cylinders through the series of bevel gears. If more power is needed then additional Magnus cylinders can be added in pairs. The belts  1021  and  1032  can be replaced with roller chain, cogged belt, v-belt, ribbed belt, or cable. Alternatively referring to  FIG. 14 , the electricity from the generator  1030  can be used in a reaction chamber  2000  for separating water into oxygen and hydrogen using the electrical current, thereby breaking water into an outflow means for the oxygen  2005  and an outflow means for the hydrogen  2010 . The hydrogen can then be stored in a pressurized bottle  2015  or oxidized directly in a conventional generator  2020 . 
         [0058]      FIG. 9  shows a planar embodiment of an on-axis Magnus system. When the fluid flow  520  reaches the Magnus cylinder  500  which is rotating in direction  501 , the flow is diverted around the cylinder causing higher pressure in flow stream  505  and lower pressure in flow stream  506 . The gradient of flow stream  505  and flow stream  506  results in lift  510 . Referring now to  FIGS. 10 and 11 , the energy harvester using the on-axis Magnus system of  FIG. 9  is mounted to a structure where the energy harvester is in communication with a fluid flow  90 . The energy harvester comprises side walls  307  that receive a flow  90 . The central shaft  40  with Magnus cylinders  200 ,  201 ,  210 , and  211  located thereon is mounted between the channel side walls  307 . The fluid flow path is defined by an inflow fluid channel formed by channel walls  307 . The walls can also be curved either in the side or bottom walls in this configuration and can have opposite elevations in the plane parallel to the fluid flow path. This acts as a concentrator for the fluid flow by channeling a greater volume of fluid to the energy harvester thereby increasing the speed of the fluid that will increase the lift generated by the cylinder. This intensification can be used in any of the embodiments envisioned by the present invention. 
         [0059]    Referring now to  FIGS. 12 and 13 , Magnus cylinder diameters can be sized and arranged in tandem so that the Magnus cylinders in a second energy harvester benefit from the increase in water velocity caused by an initial energy harvester. Here the dimension  700  is equal to about 10 times the Magnus cylinder diameter  701 . To increase the lift, the energy harvester is replicated within 1-20 diameters of the Magnus cylinder in the downstream direction of the flow. In any embodiment, the fluid flow  520  ( FIG. 9 ) or  9  ( FIGS. 10 and 11 ) can be hydraulic or pneumatic. 
         [0060]    In any application, the fluid flows can be the output flow streams of an effluent system. For example, the inflow fluid channel can be connected to one or more of a sewer, a water treatment facility, a water drain, a holding pond, aqueducts, a roof drain, outflow from a dam, an air conditioning line, and a holding tank. 
         [0061]    Referring to  FIG. 15  an energy harvester  405  of the present invention is attached to a barge comprised of deck  627  and pontoons  626  and  628 . The water line is shown as  622 . 
         [0062]    Referring to  FIG. 16  an energy harvester  405  of the present invention is attached to a bridge structure comprised of deck  627 ,  650 ,  655 ,  656 , and  651 . The water line is shown as  622 . 
         [0063]    Referring to  FIG. 17 , an energy harvester  405  of the present invention is attached to a bottom of the fluid channel by deck  627  and pontoons  626  and  628 . The water line is shown as  622 . 
         [0064]    Referring to  FIG. 18 , an energy harvester  3000  of the present invention having shaft  40  is connected to a generator  3030  with shaft  3005 , gears  3010  and  3015 , and shaft  3020  instead of a belt drive system as shown in  FIG. 6 . 
         [0065]    Energy harvester  405  can also be connected directly to a device such as a sensor to provide power for the sensor. Typical applications include weather sensors, wave sensors, and under water current sensors. 
         [0066]    The energy harvester can be attached to either a floating platform or a fixed platform depending on the conditions of the fluid that it is placed in. 
         [0067]    Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the appended claims.