APPARATUS FOR RECOVERING WAVE ENERGY

The present invention relates to an apparatus for the recovery of wave energy according to the preamble of claim 1 and to an equipment for the recovery of wave energy according to the preamble of claim 9.

In a certain depth near the bottom of a water basin, in the so-called intermediate water area, the water mass motion caused by waves is mainly reciprocating, i.e. the water mass points perform hardly any up-and-down motion. Upon transferring towards the surface of the water basin, the longitudinal profile of the water mass tra- jectory becomes more and more circularly elliptical, and finally circular. The intermediate water area refers here to the same area as in the PCT publication FI2004/000240, i.e. to the water basin area, generally ocean area in the depth range of the so-called breaker-line and shallow waters, extending to the wavelength L of 0.5. In the intermediate water area the relation of the water depth h to the principally prevailing wavelengths L is between 1/2 — 1/20.

In the state of the art there are known several different apparatuses for the recovery of wave energy, but they have the drawback that their energy production capacity is poor, if they were used for the recovery of wave energy especially from the motion of water masses caused by surface waves in the intermediate water area. An exam- pie of such an apparatus is an energy production apparatus disclosed in the document WO 98/17911 (Lombardo et al.), which is fastened to the bottom of the water basin near the coast, in which a sheet moving along with the water mass would recover only a small part of the kinetic energy of the water mass, if it were transferred to the intermediate water area.

The purpose of the present invention is to eliminate the drawbacks of the state of the art. Thus, it is an object of the invention to achieve an apparatus for the recovery of wave energy that is primarily located in the intermediate water area of the water basin, at the bottom, with which it is possible to efficiently recover the energy of the reciprocating motion of the water mass.

The object of the invention mentioned above will be achieved by the apparatus for the recovery of wave energy according to claim 1 and by the equipment for the recovery of wave energy according to claim 9.

The apparatus for the recovery of wave energy according to the invention is fastened to the bottom of the water basin, and it comprises a primary recovery unit for wave energy, a part moving by the action of the water mass motion caused by waves, and a lever system transmitting kinetic energy from the said moving part to the primary recovery unit. The part moving by the action of the water mass motion is a platelike element, which is arranged to move essentially vertically by the action of the water mass motion by articulating the element to the lever system in the halfway of the length of its vertical axis so that the main kinetic component of the water mass will always be approximately at the same angle in relation to the plane of the platelike element surface.

In this connection, the main kinetic component of the water mass refers to the direction of motion of the reciprocating motion of the water mass at that particular moment.

In an advantageous embodiment of the invention, the moving part is a platelike element, which is arranged to move essentially vertically by the action of the water mass motion. In this case, the main kinetic element of the water mass will always be at the same angle in relation to the plane travelling through the sheet.

The invention also relates to an equipment for the recovery of wave energy, fastened to the bottom of the water basin, and with at least two functionally intercon- nected apparatuses for the recovery of wave energy.

The apparatus or equipment for the recovery of wave energy preferably comprises a part moving by the action of the wave motion and a primary energy recovery unit placed entirely below the surface of the water basin, preferably to the intermediate water area of the water basin.

The invention is based on that the energy of the mainly reciprocating motion of the water mass will be recovered by means of a platelike piece, which moves entirely with the motion of the water mass. The platelike piece is arranged to move in the vertical position, i.e. so that the angle of the vertical axis of the platelike piece does not essentially change in relation to the direction of motion of the water mass, in which case as much energy as possible can be recovered from the reciprocating motion of the water mass.

In a second advantageous embodiment of the invention the upper section of the platelike element includes a lightening element, the lower section including a weight element. In this way the centre of gravity of the platelike element can be

produced to the lower section of the sheet, in which case it will better stay in the vertical position, which is optimal for the energy collection function.

In a further advantageous embodiment of the invention the platelike element is articulated to the lever system in the halfway of the length of its vertical axis. In this way, the vertical component of the path of the articulated platelike element can be made as small as possible, and the centre of gravity will be below the articulated point.

In this application, the primary energy recovery unit refers to the intermediate or final storage of energy, into which the kinetic energy arriving from the mechanic lever system will first be recovered. If the kinetic energy will be transferred further, for example, from several primary energy recovery units in the equipment for the recovery of wave energy to be assembled to a shared energy storage, this energy storage will be called a secondary energy recovery unit.

In the US application 2004/0007881 there is disclosed a wave energy recovery ap- paratus, in which, due to their structure, the apparatuses according to Figures 1-3 do not move vertically in relation to the main kinetic component of the water mass, and the moving parts according to Figures 4 and 5 have been articulated from their lower ends to the base and, at least from one other point to the primary energy production apparatus. The articulation point to the primary energy production apparatus varies, and it is not mentioned in the specification that this point could be in the middle axis of the moving part. The reason for this could be that the moving parts shown in Figures 4 and 5 have been articulated to the base from at least one point in addition to the articulation point located in the middle axis, in which case their efficiency will remain relatively insignificant. Only the apparatus alternative illustrated in Figure 4 could stay in the vertical position in relation to the main kinetic component of the water mass, the component extending essentially horizontally in the intermediate water area. However, the efficiency of such an apparatus will remain low, due to the way the moving part is articulated both to the base and to the piston-type energy production apparatus. Further, contrary to the invention, the apparatuses in Figures 4 and 5 are not platelike; the inventors have observed that the platelike shape of the moving part is the most advantageous for the energy production efficiency.

The apparatus disclosed in the patent specification GB 159 6053 again floats constantly in the immediate vicinity of the surface, due to its pontoons, and the equip- ment is anchored to the bottom by a wire. Further, the equipment always has at least

two parts moving with the water mass, which parts are connected to each other, and it is mentioned that they receive energy both from the vertical and horizontal motion of the water mass. Due to the manner the equipment recovers energy, the floating sheets recovering energy are not connected to each other on the middle axis. Be- cause the equipment has not been fastened to the bottom in a fixed manner as in the present invention, it is not able to efficiently recover energy of the water mass moving in the intermediate water area, in the vicinity of the bottom. As can be seen from Figure 4 in the specification D2, the platelike sheets 10, 11 of the equipment cannot stay in the vertical position in relation to the main direction of the water mass mo- tion, for example, due to the articulation point of the sheets 10, 11 to the rod 51 connecting them, and due to the equipment floating near the surface. In the illustrated equipment, the sheets "hang" on the pontoon, and they tilt occasionally along with the motion of water, being sometimes in the vertical position, sometimes in an inclined position; the sheets do not actively try to find the best position in relation to the water mass motion as in the present invention.

Other advantages and embodiments of the invention will be evident from the enclosed claims and the description of the advantageous embodiments of the invention.

The invention will next be illustrated in more detail by referring to the enclosed drawings, in which

Figure 1 is a side view of a single apparatus for the recovery of wave energy according to the present invention;

Figure 2 is a perspective view of an equipment for the recovery of wave energy according to the invention, with three wave energy recovery apparatuses,

Figure 3 is a perspective view of a variation of a platelike element used in the appa- ratus of the invention for the recovery of wave energy; and

Figure 4 is a cross-sectional view illustrating the position of the energy recovery unit of the invention at the bottom of a water basin.

An individual energy recovery apparatus handled in this application or an energy recovery equipment consisting of several functionally interconnected energy recov- ery apparatuses is placed onto the bottom of a water basin, such as ocean, in a manner shown in Figure 4. The figure illustrates diagrammatically an energy recovery apparatus 1, the fastening point of which is located in the depth h from the water surface S at the bottom B of the ocean. The apparatus for the recovery of wave en-

ergy can be fastened integrally to the bottom of a water basin, such as ocean, either directly or preferably indirectly by means of a suitable fastening arrangement, such as a base plate, as will be explained later.

The apparatus is located in the so-called intermediate water area, in which waves with the wavelength L generated by generally prevailing wind conditions cause the water mass points to move in the vicinity of the bottom B either reciprocally or in the form of a very narrow ellipse. The recovery apparatus 1 is fastened to the bottom with a conventional technique known in the anchoring of underwater constructions; for example, by poles to a sedimentary bottom or by special connecting blocks to a rock bottom. An energy recovery equipment consisting of several recovery apparatuses can again be fastened to the bottom B by means of lattice or concrete structures. The apparatuses 1 shown in the figure are located in the depth L/2 from the surface of the water basin, and entirely below the surface in generally prevailing wind conditions. Figure 1 illustrates in a more detailed manner one em- bodiment of the energy recovery apparatus 1 of the invention. The recovery apparatus 1 comprises a primary energy recovery unit 3 and a sheet 2 moving by the action of the wave motion, with a two-piece lever system 5 provided between them. By the action of the wave motion, water mass moves on the installation site of the energy recovery apparatus (in the intermediate water area at the bottom of the water basin) back and forth in the direction of a double-ended arrow, i.e. its main kinetic component is directed either perpendicularly to the right or perpendicularly to the left.

The primary energy recovery unit 3 comprising a generator 33 connected to a hydraulic unit 31 is connected to the base plate 4, which is fastened to the ocean bottom in the intermediate water area on the ocean bottom. The hydraulic unit 31 has a hydraulic pump 31a (or a hydraulic cylinder 31a) connected to the lever system 5, which drives a hydraulic motor 3 Ib. The hydraulic motor 3 Ib rotates the generator 33, the electric current obtained from which can be directed, for example, to a secondary energy recovery unit above the water surface.

The hydraulic pump 31a of the recovery unit 1 is connected to the rectangular metal sheet 2 moving along with the water mass motion via the lever system 5. The sheet 2 is articulated to the lever system 5 at the articulation point 5 a, which is located in the halfway of the sheet height 1. The height 1 of the sheet is at most approximately a half of the distance between the surface and bottom of the water basin at the location point of the energy recover unit 1 at the bottom of the ocean. The upper edge of the sheet 2 has a pontoon 6 extending parallel to the edge in question, which is either a separate part with a lower density than the material density of the sheet, a part

to be attached to the sheet, or a part fixedly integrated in the sheet, the density of which has been made smaller than the density of the rest of the sheet, for example, by structural properties of the part. Such a structural property can be, for example, a hollow space formed inside the part. In the lower edge of the sheet there again is a weight 7 parallel to the lower edge. The weight 7 is either a separate part to be attached to the sheet with a bigger density than the material density of the sheet, or a part fixedly integrated in the sheet, the density of which has been made bigger than the density of the sheet, for example, by structural properties of the sheet. Such a structural property may now be, for example, a filling added inside the lower edge of the sheet and made of a material, the density of which is bigger than that of the rest of the sheet material.

The lever system 5 comprises two arms 51 and 53, which are attached to each other from their first ends at the articulation point 5 a. The other end of the first arm 51 is articulated to the hydraulic pump 31a of the hydraulic unit 31. The second arm 53 of the lever system is again fastened to the metal sheet 2 moving along with the water mass. The arm 51 connected to the hydraulic unit of the lever system 5 now performs a horizontal reciprocating movement, as the sheet 2 moves by the action of the reciprocating motion of the water mass. In accordance with Figure 1, the motion of the sheet 2 has a circular path, the midpoint of the path being located on the ver- tical plane N travelling in the halfway of the extent of the path of the lever arm 51 , fastened to the hydraulic pump 3 a. The motion of the sheet 2 is conveyed from the arm 53 articulated to the halfway of the height 1 of the sheet via the articulation point 5b in its other end to the arm 51 connected to the hydraulic unit. The extent of the circular arc made by the sheet 2 depends on the intensity of the water mass mo- tion. During its circular path, the sheet 2 moves in a vertical position, due to the location of the lever arm 53 and the articulation point of the sheet (in the halfway of the height of the sheet) and the centre of gravity Pl of the sheet (the centre of gravity Pl being located in the lower part of the sheet).

When the sheet 2 moves in the vertical position with the water mass, a uniform sur- face pressure, which is as big as possible, is continuously applied to its planar surface from the reciprocating water mass, and in this case the ability of the energy recovery apparatus 1 to convert wave energy into electric energy with the generator 33 is as efficient as possible. Thus, the angle of the main kinetic component of the moving water mass to the plane E of the sheet surface stays approximately the same all the time. The water mass motion caused by waves is mainly reciprocal at the installation site and in the installation depth of the energy recovery apparatus 1 of the

invention, and the speed vector of its horizontal main kinetic component (in Figure I ₅ either directly to the left or directly to the right) is approximately constant so that the amount of energy generated by the wave energy recovery apparatus per time unit stays about constant.

The invention also relates to equipment 10 for the recovery of wave energy, in which several wave energy recovery apparatuses 1 disclosed in Figure 1 have been functionally connected together. In this case, several said apparatuses 1 can be connected either physically together, for example, by means of a shared bottom plate or, alternatively, the primary energy recovery units 2 of the apparatuses can be con- nected together for achieving a more uniform energy production ability. In the embodiment of a wave energy recovery equipment 10 of the invention described in Figure 2, there are three energy recovery apparatuses 1 similar to those in Figure 1 , connected together from their primary energy recovery units. The equipment 10 is fastened to the ocean bottom B by a gravitation or pile foundation. By placing the sheets 2; 2', 2", 2'" of the individual recovery units 1; 1 ', 1 ", 1 '" moving with the mater mass at a suitable distance from each other, it is possible to achieve a phase shift between the moving parts of the hydraulic units and, at the same time, to the electric current generated by the generators. Thus, the electric current taken out from such a system has a more uniform quality than what the electric current ob- tained from merely one recovery unit would be. The primary energy recovery units of the recovery apparatuses V, 1", 1'" can be connected together either under water, or electric current can be directed from them by means of suitable wirings to a secondary energy recovery unit located on the surface.

The apparatuses 1 for the recovery of wave energy included in the recovery equip- ment illustrated in Figure 2 are otherwise similar to those in Figure 1, but their metal sheets 2 moving by the action of the water mass are provided with angle stops at the articulation points of the lever system and the said sheet, the structure of the angle stops becoming evident best in Figure 3. The purpose of the angle stop 55 is to prevent the angle between the arm 53 connected in an articulated manner to the moving sheet 2 of the lever system and the plane of the said sheet from becoming too small, for example, due to a single wave, which is bigger than usual. Figure 2 further illustrates how the recovery equipment is provided with tanks 8, which can be filled with air for raising the recovery equipment 10 to the surface of the water basin for servicing.

Above there have only been disclosed some embodiments of an apparatus or equipment for the recovery of wave energy according to the invention, and it will be

obvious for one skilled in the art that it is possible to realise the invention in many other ways within the scope of the inventional idea disclosed in the patent claims.

Thus, in one advantageous embodiment of the invention, the operation of the sheet 2 is optimised by connecting it to the lever system 5 from one point via the arm 53. The articulation point 5a of the arm 53 and the metal sheet 2 is located about halfway along the longitudinal axis of the metal sheet so that the upper and lower surface areas of the articulation point are identical. When the lower end of the metal sheet is still provided with the weight element 7 and the upper end with the pontoon 6, the metal sheet 2 will swing slightly around its articulation point 5 a in the hori- zontal direction while performing circular rotating motions around the articulation point 5b. The free, horizontally moving upper and lower ends 6,7 of the metal sheet 2 thus search continuously for their correct position in the reciprocating water mass.

List of reference numbers

1 apparatus for the recovery of wave energy

1 ' , 1 " , 1 " ' apparatus for the recovery of wave energy

2 part moving with the water mass

2 ' , 2 " , 2 " ' part moving with the water mass

3 primary energy recovery unit

31 hydraulic unit

31a hydraulic pump

3 Ib hydraulic motor

33 generator

4 bottom plate

5 lever system

5 a articulation point

5b articulation point

51 lever arm connected to the recovery unit

53 lever arm connected to the sheet

55 angle stop

6 lightening element

7 weight element

8 tank

10 equipment for the recovery of wave energy

h height of the water basin

1 length of the part moving with the water mass in elevation

B bottom of the water basin

E surface of the platelike element

N vertical plane

P 1 centre of gravity of the plate

S surface of the water basin

T intermediate water area