The present invention relates to a new concept for obtaining energy from ocean waves. It involves at least 2, preferably 3, attaching devices called arm devices, between 2 structures, one of which is anchored and one of which—typically called a heave structure—is moved by the waves. Providing 3 arm devices, comprising 3 joints and 2 arms between 2 structures, is the ideal configuration.
Definitions: A revolute joint is also called a rotational joint. A prismatic joint is also called a sliding joint. An arm is the tubular structure attached on each side to a joint. An arm device refers to the combination of 2 arms and 3 joints. The 3 joints provide 3 degrees of movement freedom—that is, 3 joints at which movement can occur.
There are several categories of invention for obtaining energy from ocean waves. One of the most efficient types has been the heave variety, one of which is known as Salter's duck, shown in
The present application is in the heave category of wave energy converters. So it is worthwhile to understand how the classic heave converter, Salter's Duck, works. The following quotation is from https://science.howstuffworks.com/environemtnal/green-science/salters-duck1.htm “Salter's Duck is just one of many concepts for a wave energy converter (WEC), which can potentially convert wave power to usable energy . . . . The Duck itself is shaped like a teardrop, and many of these “teardrops” attach to a long spine to make up the whole Salter's system. The nose of the teardrop faces incoming waves and bobs as they pass. Essentially, this involves a transfer, or “capture,” of the wave's energy. In theory, this bobbing action would capture as much as 90 percent of the wave's massive energy, and uses that energy to keep pistons running. The pistons in turn pressurize hydraulic oil. When pressurized enough, the oil enters a hydraulic motor, which generates electricity [source: Stuart]. The system would theoretically use 90 percent of the captured energy. This high efficiency makes the Duck the Holy Grail of WECs.”
This application has a novel method for addressing one of the deficiencies of that standard: that it has poor adaptation to changes in wave height. Since wave energy is proportional to the height squared, the inability to extend beyond a limited range is a deficiency in efficiency that becomes more glaring the greater the variation in wave height.
The Salter duck transduces the wave energy by using 4 gyroscopes that move with the wave motion and create hydraulic energy. Salter showed in U.S. Pat. No. 4,300,871 how the gyroscopes work. The gyroscopes are arranged in pairs to get energy from opposite directions of movement. Each gyroscope drives a hydraulic pump which then drives a hydraulic circuit which then drives an electric generator. FIGS. 1-3 of U.S. Pat. No. 4,300,871 show how it works. The claims state this clearly.
Another patent by Salter, U.S. Pat. No. 3,928,967, states, “In order to convert the pivotal motion of the wave removing member into useable energy, a pump such as a variable stroke rotary pump having a stator fixed relative to the supporting member and having a rotor which turns with the energy removing member can be provided. In such pumps. hydraulic bearings can be utilized.”
Gyroscopic power conversion is known.
A related device is the category of oscillating wave surge converter. These devices typically have one end connected to a structure or the seabed while the other end is free to move. The arm oscillates as an inverted pendulum mounted on a pivoted joint in response to the movement of water in the waves. Energy is collected from the relative motion of the body with respect to the connected point.
Surface attenuators operate to some extent by heave. Attenuator devices are relatively long in length (up to 150 m) as compared to ocean wavelengths, and are typically positioned in parallel to the general direction of wave propagation. Attenuators consist of multiple buoyant segments that articulate as wave crests and troughs pass. Mechanical energy is extracted from the relative motion of each segment, usually though the compression of a fluid in hydraulic pistons. Attenuators can be designed to float freely and operate at the water's surface or can be arranged to articulate in reaction to a connected structure attached to the ocean floor. The most notable surface attenuator WEC is the Pelamis. These systems are very inefficient.
Another example of a heave structure is U.S. Pat. No. 9,169,823 B2. It is a device for generating electricity that includes a buoyant structure, a heave plate, at least one load carrying structure that is mechanically coupled to both the buoyant structure and the heave plate, and at least one magnetostrictive element. The magnetostrictive element is configured to experience force changes applied by the load carrying structure caused by hydrodynamic forces acting on the device. It is shown in
WEC U.S. Pat. No. 9,169,823 B2—The device uses a floating buoyant structure which is attached to a heaving plate by magnetostrictive elements and load carrying elements. The floating structure has 3 points of connection to the heaving plate. The device has a cylindrical buoy as floating structure. The device uses a heave plate in order to damp the heave response of the body.
The force changes in the load carrying structures between the heave plate and the float create current flow in the magnetostrictive elements.
Current Application—We use a floating structure which is attached to a base plate using mechanical linkages such as sliding or rolling joints. The floating structure has 3 points of connection to the base plate. We use any appropriate shape as a floating element. We connect the base plate either by using a pile attached to the seabed or by using mooring lines. The movement of the hydraulic pistons due to the relative movement of the float with respect to the base plate creates pressurized fluid which can be used to produce power, but we are not limited to that way of generating power.
U.S. Pat. No. 4,631,921 describes, as shown in
WEC 4,631,921 The device has a conical floating structure which is attached to a generator via a shaft. The conical structure has 3 points of connection to the floatation system.
The device has a conical buoy as floating structure. The device uses hydraulic turbines to generate power.
Our Device—We use a floating structure which is attached to a base plate using mechanical linkages such as prismatic or rolling joints. The floating structure has 3 points of connection to the base plate. We use a triangular structure as a floating element. We use hydraulic pistons to pump hydraulic fluid into turbine.
Current technologies utilize either one or two degrees of freedom of the wave in order to harvest the energy. A device having three degrees of freedom in a connected plane is the ideal way to harness energy for heave, surge, and pitch, as the device can adjust and orient itself according to the wave characteristics. In this device, there a moving platform connected to a base (or, fixed) platform via three arm devices (or, kinematic chain) each of single degree of freedom consisting of a trio of revolute, “R”, (rotational) or prismatic, “P”, (sliding) joints. Consequently each of the independent kinematic chains can be denoted by a set of three letters indicating the succession of joints starting from the ground. A revolute joint (also called pin joint or hinge joint) is a one-degree-of-freedom kinematic pair used in mechanisms. Revolute joints provide single-axis rotation function used in many places such as door hinges, folding mechanisms, and other uni-axial rotation devices. A prismatic joint provides a linear sliding movement between two bodies, and is often called a slider, as in the slider-crank linkage. A prismatic joint can be formed with a polygonal cross-section to resist rotation. For example, if a serial chain is PRR, there is a prismatic joint at A and there are two revolute joints at B and C (joint connected to the moving platform) respectively, in
It was found by simulation that the best position of the device is for the heave structure to be immersed into the water such that the incoming wave height completely submerges its top surface.
The invention can be customized to the prevailing wave situation in each area in the process of design for a particular area according to the area's wave height, as the flow chart in
The present invention successfully addresses the shortcomings of the presently known configurations by providing a 3-points-of-freedom device to obtain energy from waves. The energy is transformed into useful form through hydraulics or circular motion in most cases.
It is now disclosed for the first time a system for obtaining energy from a wave in a body of water, comprising:
a base structure, with at least two sides, fixed to a base in or adjacent to waves,
a floating heave structure, with at least two sides, said heave structure substantially submerged by the water,
at least two arm devices, each arm device comprising:
In one embodiment, the system further comprises at least one said generator system comprises a hydraulic mechanism containing a compressible fluid, said fluid compressed by the motion of the arms and joints.
In one embodiment, the system further comprises at least one arm device comprises an electric generator, operating from rotational motion of any of the arm's revolute joints.
In one embodiment, the base structure is below the heave structure.
In one embodiment, the base structure is between an upper part of the wave on the surface and a lower part of the wave, beneath the surface.
In one embodiment, the base structure is adjustable in height above a sea floor of the body of water while fixed to a supporting object.
In one embodiment, a second heave structure is attached by said three arm devices to a second side of the base structure.
In one embodiment, the heave structure is substantially planar.
In one embodiment, the heave structure is a polygonal structure
In one embodiment, at least one part of the heave structure is concavely cupped in an area of impact of the wave on the heave structure,
In one embodiment, a length of the heave structure is equal to or a little greater than a wavelength of the wave.
In one embodiment, the heave structure is at least partially hollow.
It is disclosed for the first time a method for constructing a system to harvest energy from a wave in a body of water, comprising:
In one embodiment, it comprises at least 3 arm devices.
In one embodiment, during an initial construction of the system in the process of project design, it further comprises the steps of:
obtaining data comprising height of waves in a particular location over time,
determining a standard wave height, based on one of a group of average, median, or mode of the wave heights in a designated area,
setting the fully extended height of the arm devices for said location as at least double the standard wave height.
The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:
The principles and operation of a wave energy converter according to the present invention may be better understood with reference to the drawings and the accompanying description.
Referring now to the drawings,
A base structure does not necessarily have to be below the heave structure.
In
Clearly, the base plate needs to be fixed at the time that the heave plate is moving. However, its height from the sea floor can be adjustable. There are many reasons to adjust it, such as taking advantage of higher waves, adjusting to differences in surface height during tides, or purposely submerging it during dangerous storms.
The current invention can transfer the energy from the wave converter into useful electrical energy in at least three ways, each of which is prior art:
1. Gyroscopes. This is the method of Salter's Duck.
The current application is a heave mechanism, in the same family as the Salter duck. The methods of obtaining energy from the Salter duck have already been specified clearly in his patents and are enabling for anyone wishing to use the same system.
2. Typical permanent magnet generators at each joint. Since each joint moves back and forth, it is advantageous to change that back and forth motion into unidirectional motion. One way to do that is to use a combination of clutches and bevel gears.
3. Hydraulics. At each rotation or “prismatic” motion of the arms, they can push against hydraulic fluid, which then drives a generator.
An older method of using hydraulics is the Cockrell's Raft, referred to in patent GB1,448,204, uses a similar concept. It states in the abstract from that patent: “Apparatus for extracting energy from the wave movement of the sea comprises two or more buoyant members 11 which are hinged one to another, the members together defining a substantially continuous lower surface, and means connected between each two buoyant members for converting relative movement of the members into useful energy. As shown, the means connected between each two buoyant members comprises a hydraulic or pneumatic device 12 which transmits pressure pulses to means such as a reservoir (not shown). The apparatus can be positioned off shore and can be used to pump water to a reservoir which can be used for powering a shore based hydro-electric installation.”
While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made.
Number | Date | Country | Kind |
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62553851 | Sep 2017 | US | national |
This patent application is the continuation in part of U.S. patent application Ser. No. 16/643,565 and claims the benefit of U.S. Provisional Patent Application No. 62/553,851, entitled Wave Energy Harvester with 3 Points of Freedom, filed Sep. 3, 2017.
Number | Date | Country | |
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Parent | 16643565 | Mar 2020 | US |
Child | 17183371 | US |