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The present invention relates to a new concept for obtaining energy from ocean waves. It involves at least 2, preferably 3 mechanisms of attachment called arm devices, between 2 structures, one of which is moved by the waves. These arm devices ideally comprise 3 joints and 2 arms. Providing 3 arm devices 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.
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
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
U.S. Pat. No. 4,631,921 describes, as shown in
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, 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 motion in most cases.
It is now disclosed for the first time a system for obtaining energy from waves, 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, at least two arm devices, each arm device comprising:
a base joint of either the prismatic or revolute types attached to a side of the base structure facing the heave structure,
a heave joint of either the prismatic or revolute types attached to a side of the heave structure facing the base structure, said heave joint corresponding substantially to positions of the base joints on the base structure,
each base joint is attached to a base arm,
each heave joint is attached to a heave arm,
each pair of base and heave arms is attached to a middle joint;
each said arm device is connected to at least one generator system, said generator system defined as any mechanism that results in energy production, such as hydraulic or electrical, from the motion of the arm device.
In one embodiment, the system further comprises 3 arm devices.
In one embodiment, the system of 2 or 3 arm devices further comprises at least one generator system comprising a hydraulic mechanism containing a compressible fluid, said fluid compressed by the motion of the arms and joints.
According to another embodiment of the system of 2 or 3 arm devices, at least one arm device comprises an electric generator, operating from rotational motion of the joint.
According to another embodiment of the system of 2 or 3 arm devices, the base structure is below the heave structure.
According to another embodiment of the system of 2 or 3 arm devices, the base structure is between the upper part of the wave on the surface and the lower point of the wave, beneath the surface.
According to another embodiment of the system of 2 or 3 arm devices, the base structure is adjustable in height above the sea floor while fixed to a supporting object.
In one embodiment, the system further comprises a second heave structure attached by arm devices to a second side of the base structure.
According to another embodiment of the system of 2 or 3 arm devices, the heave structure is substantially planar.
According to another embodiment of the system of 2 or 3 arm devices, the heave structure is a polygonal structure.
According to another embodiment of the system of 2 or 3 arm devices, at least one part of the heave structure is concavely cupped in the area of impact of the wave on the heave structure,
According to another embodiment of the system of 2 or 3 arm devices, a length of the heave structure is equal to or a little greater than the wavelength of the wave. (This may be a more efficient configuration.)
According to another embodiment of the system of 2 or 3 arm devices, the heave structure is at least partially hollow.
It is now disclosed for the first time a method for constructing a system to harvest energy from waves, comprising:
providing a base structure, with at least two sides, fixed to a base in or adjacent to waves,
providing a floating heave structure, with at least two sides,
providing at least two arm devices, each arm device comprising:
a base joint of either the prismatic or revolute types attached to a side of the base structure facing the heave structure,
a heave joint of either the prismatic or revolute types attached to a side of the heave structure facing the base structure, said heave joint corresponding substantially to a position of the base joint on the base structure,
each base joint is attached to a base arm,
each heave joint is attached to a heave arm,
each pair of base and heave arms is attached to a middle joint;
each arm device is connected to at least one generator system, said generator system defined as any mechanism that results in energy production, such as hydraulic or electrical, from the motion of the arm device.
In one embodiment, the system further comprises at least 3 arm devices.
According to another embodiment of the system of 2 or 3 arm devices, the method further comprises:
obtaining wave 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 a particular 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 way in which the current invention produces useful energy is not the focus of this application. Clearly, cables connected to gears and the use of compressed fluids can convert the motion of the wave harvester into useful mechanical energy and/or pressure and then electricity.
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 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.
Filing Document | Filing Date | Country | Kind |
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PCT/IL2018/050957 | 8/29/2018 | WO | 00 |