This disclosure relates to a wave energy converter that converts wave energy into useful energy such as electrical energy.
The use of wave energy converters that convert wave energy into electrical energy or other useful energy is well known. Many different designs of such wave energy converters exist.
Waves occur at a spectrum of periods with different amplitudes at each period. Existing wave energy converters work continuously to create “resonance” with the changing waves to maximize their energy extraction. Creating resonance with waves requires changing the dynamic response characteristics of the wave energy converter, which adds complexity to the system.
One known technique for creating resonance is to use electrical tuning of the power take off system and diverse control schemes to change the converter's dynamic response characteristics. Although electrical tuning systems enhance energy extraction, they come with associated cost, weight, reliability, and maintainability challenges.
A wave energy converter is described that can change shape to mechanically tune itself to change the amount of water that the converter pushes up and down. In effect, the wave energy converter employs variable virtual added mass to tune the wave energy converter to the waves, thereby increasing the energy extraction from the waves.
The described shape change of the wave energy converter can be used separately from or to augment electrical tuning The shape change or variable virtual added mass type system described herein can be employed on any type of wave energy converter including, but not limited to, point absorber wave energy converters.
In one embodiment, the wave energy converter includes a float that has a first or standard float area. A means is connected to the float that is configured to selectively and controllably increase the standard float area. In a top plan view, the means is disposed to the side of the float such that in the top plan view, the area of the float can be selectively and controllably increased. The means can have any configuration that is suitable for selectively and controllably increasing the standard float area or the top plan view area that is acted on by the water. The means permits mechanical tuning of the wave energy converter by altering its area, and thereby changing the amount of water that is pushed up and down by the float under wave action.
In one embodiment, the area can be modulated intermittently in response to the bulk condition or state of the sea. In another embodiment, the area can be modulated frequently in response to individual waves.
In another embodiment, a wave energy converter includes a float having a float area, and a shape change means is attached to the float that is selectively and controllably actuatable to increase the float area that is acted on by the water.
In another embodiment, a wave energy converter includes a float having a float area, and a shape change mechanism is attached to the float. The shape change mechanism includes a plurality of flaps that are selectively and controllably actuatable between a fully open position and a fully closed position to increase the float area that is acted on by the water.
In still another embodiment, a method of mechanically tuning a wave energy converter includes selectively and controllably changing the shape of a float using a shape change mechanism connected to the float to change the amount of water that the converter pushes up and down.
As described further below, a shape changing or virtual added mass wave energy converter is described that can change shape to mechanically tune the wave energy converter to change the amount of water that the converter pushes up and down. In effect, the wave energy converter employs variable virtual added mass (from the change in the amount of water being forced up and down) to tune the wave energy converter to the waves.
In general, the wave energy converter can include a float of some form that has a first or standard float area. A shape change means is connected to the float that is configured to selectively and controllably increase the standard float area. In a top plan view, the shape change means is disposed to the side of the float such that in the top plan view, the area of the float that is acted on by the water is selectively and controllably increased. The shape change means can have any configuration that is suitable for selectively and controllably increasing the standard float area or the top plan view area that is acted on by the water. By changing the area of the float, the amount of water that is pushed up and down by the float under wave action is changed. In addition, if the shape change means fails, the converter still functions because the float will still work.
The shape change or virtual added mass type system described herein can be employed on any type of wave energy converter system. The examples described below utilize point absorber wave energy converters. However, other types of wave energy converter systems can be utilized.
With reference initially to
The float 12 includes a central opening 16 through which a mast 18 extends. The float 12 moves up and down on the mast 18 relative thereto. This relative movement is used to generate electricity in a known manner. The construction and operation of the float 12 described so far is conventional.
A shape change means 20 is connected to the float 12 so that the shape change means 20 is disposed under the water surface 14 with the bottom half of the float 12. In this example, the shape change means 20 is in the form of a panel mechanism that includes a series of panels or flaps 22 with orientations that can be selectively controlled. The shape change means 20 surrounds the float 12, with an inner support ring 24 that is fixed to the float 12 by supports 26, an outer support ring 28, and radial supports 30 that connect the inner ring 24 and the outer ring 28.
The flaps 22 have upper ends that are pivotally mounted to the inner ring 24 and the outer ring 28 via pivots 29 (see
With reference to
Each actuator 32 is oriented substantially perpendicular to the heave action of the float 12. In this way, the actuator 32 does not have to be particularly strong since it only has to actuate the flap actuating mechanism 31.
By extending and retracting the actuators 32, the orientation of the flaps 22 can be changed by the flap actuating mechanism.
In one embodiment, the flaps 22 remain in the selected orientation during both upward movement of the float 12 and downward movement of the float. However, it is possible to vary the flap orientation during the upward and downward strokes.
In addition, because the shape change means 20 and the flaps 22 are divided into sections, the orientations of the flaps 22 need not be the same. For example, as illustrated in
With reference to
Many different constructions of shape change means can be utilized. For example, with reference to
The virtual mass that is added is determined by the increased top plan view area of the converter that is added by the shape change means, which changes the amount of water that the converter pushes up and down. In one embodiment, when the shape change means is in the fully deployed or fully closed orientation, the shape change means adds an area approximately 2 to 4 times the area of the float. In another embodiment, the shape change means adds an area approximately 2.5 times the area of the float.
The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.
Number | Date | Country | |
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61774701 | Mar 2013 | US |