Abstract:
A wave power plant is disclosed which has one or more foils that are pivotally movable about a body. The foil is set into an oscillating, pivotal motion about the body by the force of the waves. A power engine is mounted between the body and the foil and extract works as the foil pivots about the body. The foil and body are held submerged below the surface of the water to reduce the effects of extreme weather conditions on the structural components.

Description:
BACKGROUND INFORMATION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a wave power plant. 
         [0003]    2. Discussion of the Prior Art 
         [0004]    Wave power plants are known in a number of embodiments, which oftentimes exploit the alternating heights of waves. Best known are possibly the so-called tapered channel plants, oscillating fluid columns, and float-based pumps. What they have in common is that they oftentimes comprise relatively complex structures that are relatively costly, both in terms of installation, operation, and maintenance. Such structures have large and complicated surface structures that are exposed to the elements and, thus, may be severely affected by weather conditions. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The object of the invention is to remedy or reduce at least one of the disadvantages of the prior art. 
         [0006]    This object is achieved by providing a wave power plant, in which a submerged foil is pivotally supported about a body, and wherein the foil is structured so as to be set into a swinging or oscillating pivotal motion about the body. The body is pretensioned and is provided with a plurality of foils. A power engine, which is connected between the foil and the body, is structured so as to deliver power by means of the pivotal motion of the foil. 
         [0007]    The foils are submerged and located below the water surface, for example, at 0.5 to 3 meters below the water surface. As a result, the foils are affected by the rolling motion of the waves, but their exposure to extreme weather conditions and other impacts is insignificant, compared to the exposure and its affects on equipment above the surface of the water. 
         [0008]    The foils may be formed having any suitable shape, but a relatively elongated, teardrop-like cross section appears to provide the best degree of efficiency. 
         [0009]    The body may be stretched across a cove or a strait. It is relatively simple to anchor the body on the shore, particularly when the shore is comprised of rocks. 
         [0010]    The body may be connected to one or more stays, wherein one end portion each stay is connected to the body and the opposite end portion is anchored or fastened to the seabed. The stay is structured so as to keep the body at the desired depth and also to allow the stay to withstand torsional forces exerted on it by the body. 
         [0011]    The stay may be hingedly connected to the foil and extend down to an anchor or fastener secured in the seabed, to prevent the foils from pivoting 180 degrees about the body. 
         [0012]    The body may comprise a wire, a pipe or another suitable stay, and may comprise several parallel and separately extending portions. 
         [0013]    The power engine may include a pump system, preferably a hydraulic pump connected to a hydraulic motor, whereby the hydraulic motor drives an electric generator. Advantageously, the hydraulic motor and the generator may be located onshore. 
         [0014]    If appropriate, the power engine in the foil may be an electric generator. 
         [0015]    A device according to the invention is able to exploit wave energy, even in areas close to land, and at a reasonable cost. Given that the active components are submerged, the device is only insignificantly exposed to extreme weather conditions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawings are not drawn to scale. 
           [0017]      FIG. 1  is a schematic illustration, showing the wave power plant according to the invention, wherein the power plant is stretched across a cove. 
           [0018]      FIG. 2  is a cross-sectional illustration of a body anchored to the seabed. 
           [0019]      FIG. 3  is a cross-sectional view of a power engine disposed within a foil. 
           [0020]      FIG. 4  is a cross-sectional view of a power engine in an alternative embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be complete and will fully convey the scope of the invention to those skilled in the art. 
         [0022]      FIG. 1  illustrates a wave power plant  1  stretched across a cove  10  and anchored at each end  6  and  8  to the shoreline. The wave power plant  1  comprises a plurality of foils  4  that are pivotably mounted on a body  2 . In this particular embodiment, the body  2  comprises a pipe that is pretensioned between two fasteners or anchors, a first fastener  6  and a second fastener  8 . As shown, the fasteners  6 ,  8  are located at either side of the cove  10 . The body  2  is pretensioned between the fasteners  6 ,  8  by means of a tension device (not shown), for example, in the form of a tackle or a hydraulic cylinder, and the fasteners  6 ,  8  are constructed so as to be able to withstand tensional forces as well as torsional forces. 
         [0023]      FIG. 2  shows a stay  12  that couples the body  2  to a stay fastener  16 . A first end of the stay  12  is connected in a torsional-stiff manner to the body  2  and between two foils  4  and a second end anchored to a seabed  14  by means of the stay fastener  16 . 
         [0024]      FIG. 3  shows a drive or power engine  18  disposed between the body  2  and each of the foils  4 . In this embodiment, the power engine  18  is a hydraulic pump. The body  2  extends through a bore  20  in the foil  4 . A sleeve  22  is attached to the body  2  and encircles it. The sleeve  22  has a relatively large outer radius over a first circular sector  24  and a smaller radius over a second circular sector  26 . The first circular sector  24  is provided with sector gaskets  28  arranged so as to be able to seal the bore  20 . 
         [0025]    A wing  30  with a wing seal  32  is disposed in a movable manner in a wing slot  34  in the foil  4 . The wing  30  is constructed to as to allow it to seal against the second circular sector  26 . The wing  30  is pretensioned by means of at least one spring  36 . The wing  30  divides a space, which is formed between the bore  20  and the second circular sector  26 , into a first pump chamber  38  and a second pump chamber  40 . A supply pipe  42  and a pressure pipe  44  extend within a cavity  46  in the body  2  and are connected to a hydraulic pump onshore. The two pump chambers  38 ,  40  communicate with the supply pipe  42  and the pressure pipe  44  via check valves  50  and conduits  52 . The pump chambers  38 ,  40  are sealed in an axial direction by sealing end walls (not shown). 
         [0026]    Referring still to  FIG. 3 , the operation of the wave power plant  1  is as follows: When a wave  54  lifts the foil  4  and causes the foil  4  to oscillate upwards, i.e. clockwise, hydraulic fluid flows in a manner known per se via respective conduits  52  and the check valve  50  from the supply pipe  42  into the first pump chamber  38 . At the same time, pressurized hydraulic fluid flows via respective conduits  52  and the check valve  50  from the second pump chamber  40  to the pressure pipe  44 . When the foil  4  pivots in the opposite direction, hydraulic fluid flows in a corresponding manner to the second pump chamber  40  from the first pump chamber  38 . 
         [0027]    The power engine  18  shown in  FIG. 3  extracts work only as the foil  4  moves upward relative to the body  2 , i.e., in one direction only. This power engine is, however, unsuitable if work is to be extracted as the foil  4  moves in different directions. 
         [0028]      FIG. 4  illustrates an alternative embodiment of the wave power plant  1 , in which work is extracted irrespective of the angle that the foil  4  assumes about the body  2 . The power engine  18  comprises a cam  56  that encircles the body  2 . Rollers  58 , which are connected to respective piston rods  62  of hydraulic cylinders  60 , bear against the cam  56  in the axial direction of the body  2 . Several hydraulic cylinders  60  may be distributed about the body  2 , insofar as a pilot pressure in a supply line (not shown) ensures that the rollers  58  bear against the cam  56  also during the plus-strokes of the piston rods  62 . 
         [0029]    Advantageously, the cam  56  may be attached to the foil  4 , and the hydraulic cylinders  60  attached to the body  2 . Axial forces due to the hydraulic cylinders  60  are supported by a bearing  64 , and a seal  66  prevents water from entering into the bearing  64 . Hydraulic liquid is pumped by means of the hydraulic cylinders  60  via valves (not shown) when the cam  56  is rotated relative to the cylinders  60 . In this alternative embodiment, the power engine  18  may work irrespective of which angle the foil  4  assumes about the body  2 . 
         [0030]    It is understood that the embodiments described herein are merely illustrative of the present invention. Variations in the construction of the wave power plant may be contemplated by one skilled in the art without limiting the intended scope of the invention herein disclosed and as defined by the following claims.