BACKGROUND

The invention relates to an arrangement for recovering wave energy- Numerous arrangements are known for recovering wave energy of water.

A problem with the known solutions is e.g. that they operate at a fairly low efficiency.

BRIEF DESCRIPTION

An object of the present invention is to provide a novel and improved arrangement for recovering wave energy.

An arrangement according to the invention is characterised in that the arrangement comprises:

at least one hollow piece which is provided with an outer casing and an inner space therein, the outer casing being engaged to be rotatable with respect to a body of the hollow piece, the inner space being provided with an inner arrangement element comprising a mechanical rectifier, a rotating axle, a gearbox, and an electric generator, the mechanical rectifier being connected to the outer casing and arranged to convert reciprocating rotational motion of the outer casing into one-directional rotational motion of the rotating axle, and the gearbox being arranged to create at least two transmission ratios between the outer casing and the rotating axle, and the electric generator coupled to the rotating axle to be rotated by the first mechanical rectifier.

The invention is based on using the gearbox for changing the gear ratio between the hollow piece receiving energy of water and the generator generating electricity. An advantage is that an optimum recovery of wave energy may be achieved.

According to an embodiment of the invention, the gearbox comprises a sun-and-planet gear. An advantage is that the gearbox is compact in its size.

According to an embodiment of the invention, the inner arrangement element is fastened to a support structure which is located outside the hollow piece and with respect to which the outer casing is arranged rotatably. An advantage is that the efficiency of the arrangement may be further increased. According to an embodiment of the invention, the inner arrangement element comprises a mass piece arranged to increase inertia of the inner arrangement element with respect to the outer casing. An advantage is that the efficiency of the arrangement may be further increased.

According to an embodiment of the invention, the hollow piece is a piece substantially cylindrical in its external shape, preferably at least substantially round in cross section of its outer surface, and that the outer surface of the outer casing is provided with a side projection resisting the motion of waves. An advantage is that the efficiency of the arrangement may be further increased.

According to an embodiment of the invention, the inner arrangement element is fixed with a pontoon that is arranged outside and at a distance from the outer casing. An advantage is that the arrangement can be arranged on the surface of the water.

According to an embodiment of the invention, the hollow piece is arranged to move with respect to the control surface and simultaneously about its longitudinal axis, which generates a mutual movement between the outer casing and the inner arrangement element, and the control surface is arranged to return the pontoon to its initial position. An advantage is that the arrange- ment can be arranged on beach to receive energy of waves coming ashore.

BRIEF DESCRIPTION OF THE FIGURES

The invention is now described in greater detail in connection with some embodiments and with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of an embodiment of an arrangement the inner arrangement element of which being removed from the inner space,

Figure 2 is a perspective view of a second embodiment of the arrangement,

Figure 3 is a side view of a third embodiment of the arrangement, Figure 4 is a side view of a fourth embodiment of the arrangement,

Figures 5a and 5b are showing a fifth embodiment of the arrangement from side and from front, and

Figure 6 is a perspective view of a sixth embodiment of the arrangement. For the sake of clarity, the figures show the embodiments in a simplified manner. In the figures, like reference numerals identify like elements.

DETAILED DESCRIPTION

Figure 1 is a schematic view of an embodiment of an arrangement the inner arrangement element of which being removed from the inner space.

The arrangement 100 comprises at least one hollow piece 1 which is provided with an outer casing 2 and an inner space 3 therein, the outer casing being engaged to be rotatable with respect to a body 8 of the hollow piece, the inner space 3 being provided with an inner arrangement element 16 com- prising a mechanical rectifier 5, a rotating axle 14, a gearbox 4, and an electric generator 9. The components of the inner arrangement element 16 are arranged preferably coaxially with a common axis X.

The mechanical rectifier 5 is connected to the outer casing 2 and arranged to convert reciprocating rotational motion of the outer casing 2 into one- directional rotational motion of the rotating axle 14, and the gearbox 4 being arranged to create at least two transmission ratios between the outer casing 2 and the rotating axle 14, and the electric generator 9 coupled to the rotating axle 14 to be rotated by the first mechanical rectifier 5.

In an embodiment, a non-rotating central axle (not shown) is ar- ranged to the common axis X, and the rotating axle 14 is arranged coaxially on and bearing-mounted in relation to the central axle. An advantage is that the assemblage of the arrangement may be simplified.

In the embodiment shown in Figure 1 , the motional energy of waves is converted into rotational motion by fins 10 that are fixed on the outer surface of the outer casing 2. The fins 10 are arranged obliquely or like screw thread in relation to the longitudinal axis of the outer casing 2.

In the embodiment shown in Figure 1 , at least one of the fin(s) 10 is/are arranged to be movable in relation to the outer surface of the outer casing 2. This has been realized by a fin hinge 25 that attaches the fin 10 rotatably to the outer casing. The alignment of the fin 10 may be controlled by a alingnment control means (not shown), comprising an actuator, such as an electric or hydraulic motor, and a control unit that operates the actuator. The control unit may be controlled e.g. via a remote control by an operating personnel or it may be a fully self-controlling unit. Thus the alingnment of the fin(s) 10 can change in relation to the common axis X of the arrangement. An ad- vantage is that the fin(s) may be arranged in a position that is most effective for recovering wave energy of water. It is to be noted, however, that all the fin(s) 10 may alternatively be attached stationary with respect of the outer casing 2.

The outer casing 2 shown in Figure 1 has a cross-section of a circu- lar cylinder surface. Of course, it may have another shape e.g. that of a polygonal, such as a triangular, tetragonal or pentagonal, cylinder, or it may have a shape other than that of a cylinder. The cross section of the outer casing 2 may substantially differ from the rotationally symmetrical shape: it may be elliptical in shape, for instance.

The hollow piece 1 is placed in water, wherein the outer casing 2 moves due to the influence of motion of the water. According to an idea, the embodiment shown in Figure 1 is especially suitable for use in tide waters or similar waters where water flows in one direction for a long time, and then turns in opposite direction.

The outer casing 2 may rotate with respect to inner arrangement element 16. The inner arrangement element 16 is fastened by e.g. supports 20 to a support structure 1 1 located outside the hollow piece 1 .

The support structure 1 1 may be secured e.g. to dry land, water bottom, a vessel, a bridge or the like. The outer casing 2 may thus rotate with re- spect to the support structure 1 1 .

The hollow piece 1 may be arranged in an open-ended turbine tube 22 that is shown by dotted lines in Figure 1 . According to an idea, the turbine tube 22 may comprise bevelled sections 22 at its ends for guiding flow of water into the turbine tube 22.

It is to be noted that in this description, the concept "outer casing" refers expressly to parts of an outer surface of the hollow structure 1 that are rotatably engaged with respect to the body 8.

The rotational movement of the outer casing 2 is transferred to the inner arrangement element 16. The rotational movement is transferred through the gearbox 4 and the mechanical rectifier 5 to the electric generator 9. The electric energy produced by the electric generator 9 is transferred out from the arrangement 100 by e.g. power cable 7 known per se.

In an embodiment, the rotational movement is transferred to the gearbox 4 and then to the mechanical rectifier 5.

In another embodiment, the rotational movement is transferred to the mechanical rectifier 5 and then to the gearbox 4. The gear ratio provided by the gearbox 4 is changed, preferably automatically, so that an optimal rotational speed of the electric generator 9 may be achieved. According to an idea, the optimal rotational speed is speed on which the electric generator 9 converts the mechanical energy most effectively to electric energy.

In an embodiment, the gearbox 4 comprises a sun-and-planet gearbox.

In another embodiment, the gearbox 4 comprises a variable-speed transmission, e.g. belt-driven variable-speed transmission.

In still another embodiment, the gearbox 4 is an automatically controlled multi-speed gearbox.

According to an idea, the gearbox 4 is able to give at least two gear ratios. However, the number of the gear ratios is preferably higher than two, for instance four to seven.

The mechanical rectifier 5 may be implemented in many ways known per se, for instance by a rectifier described in Fl Patent No. 1 12694, particularly in its Figures 2, 3, and 4 and the corresponding parts of the description, or by a rectifier disclosed in Finnish Utility Model Fl 8504.

An embodiment of the arrangement 100 the inner arrangement ele- ment 16 comprises a mass piece 12 arranged to increase inertia of the inner arrangement element with respect to the outer casing 2.

In an embodiment, the arrangement comprises an auxiliary power unit 24, such as a pneumatic muscle actuator the actuating movement of which is induced by an electrical signal. The auxiliary power unit 24 is arranged to rotate the rotating axle 14 in such situations where the movements of the waves are too weak to cause the outer casing to start its rotational movement. Thus the auxiliary power unit 24 is used for overcoming starting friction of the arrangement.

The apparatus comprises preferably two auxiliary power units 24, one of which arranged to rotate the rotating axle 14 in first rotational direction and another in opposite direction.

Figure 2 is a perspective view of a second embodiment of the arrangement.

The arrangement 100 is arranged on the surface of water and com- prises two pontoons 15 arranged outside and at a distance from the hollow piece 1 and its outer casing 2. The inner arrangement element 16 is fixed with the pontoons 15. Thus the pontoons 15 may rotate in relation to the outer casing 2. It is to be noted, that the number of the pontoons 15 may vary from one pontoon 15 to plurality of pontoons 15.

The arrangement 100 comprises a cable or wire 18 that is anchored to an immobile target, e.g. water bottom and connected to the outer casing 2.

A weight 13 is secured to an opposite end of the wire 18 and arranged to hang between the surface of water and the water bottom. As the pontoon 15 moves up and down along with the waves, the wire 18 rotates the outer casing back and forth. This rotational motion is transmitted via gearbox 4 and the mechanical rectifier 5 to the electric generator 9. This enables potential energy of waves to be recovered very efficiently.

The arrangement 100 may comprise a stabilizer fin 17 that facilitates keeping the arrangement 100 in correct alignment with respect to the waves.

Figure 3 is a side view of a third embodiment of the arrangement.

In the embodiment illustrated in Figure 5, the hollow piece 1 is arranged to move with respect to a control surface 19 which is arranged to return the hollow piece 1 to its initial position.

According to an idea, the control surface 19 may comprise a toothed rail 21 and the outer casing 2 a toothed rim 6 compatible with the toothed rail 21 and arranged on the outer surface of the outer casing 2.

The hollow piece 1 is arranged to move with respect to the control surface 19 so that it simultaneously rotates due to the influence of waves or wind, for example.

According to an idea, the control surface 19 may further be an inclined surface whose angle of inclination a may be fixed or adjustable. The control surface 19 may also be a planar surface or the surface may be of any shape allowing the hollow piece 1 to move and rotate. A mutual movement is generated between the outer casing 2 and the inner arrangement element 16 as the hollow piece 1 moves with respect to the control surface 19.

Figure 4 is a side view of a fourth embodiment of the arrangement. According to an embodiment, the inner arrangement element 16 is arranged in a second hollow piece 26 that is accommodated inside the outer casing 2. The second hollow piece 26 is fastened to a support structure 1 1 which is located outside the outer casing 2 by e.g. a support axle 31 . The support axle 31 allows the outer casing 2 to rotate thereon. Thus the second hollow piece 26 is stationary with respect the support structure 1 1 , while the outer casing may rotate with respect to the support structure 1 1 .

A rotating axle 14 is supported by bearing means 27, and it is rotated by a gearbox 4 the type of which is a sun-and-planet gearbox. The internal gear 34 of the gearbox is rotating with the outer casing 2. The rotational movement of the internal gear 34 is transferred by planet gears 33 - attached rotatably in the second hollow piece 26 - to a sun gear 32 that is fixed on an auxiliary axle 35. The rotation of the auxiliary axle 35 is transferred to a mechanical rectifier 5 and from there to a generator 9. The arrangement may fur- ther comprise a mass piece 12.

An advantage of the second hollow piece 26 is that it establishes a good mounting base for the sun-and-planet gearbox, and that a space sealed with seals 36 and containing lubricant, e.g. oil, for lubricating the gearbox may be easily created between the second hollow piece 26 and the outer casing 2. Thus the maintenance interval of the gearbox may be extended.

Figures 5a and 5b are showing a fifth embodiment of the arrangement from side and from front. In an embodiment, the hollow piece 1 is attached rotatably with respect to a water bottom WB by a bearing means 27, and the hollow piece 1 comprises a directing surface 28 for turning the hollow piece 1 in line with water movements. The bearing means 27 may be supported to a natural water bottom or an artificial structure made in the water.

The hollow piece 1 may turn in an optimal direction by water movements affecting to the directing surface 28.

In an embodiment, the hollow piece 1 comprises a tank 29 and pumping means 30 connected to the tank 29. The tank 29 may be selectively filled with water or air. When filled with air, the buoyancy of the arrangement lift the arrangement on water surface. An advantage is that the maintenance of the arrangement is easier on water surface than in underwater surroundings.

Figure 6 is a perspective view of a sixth embodiment of the ar- rangement. The arrangement comprises the bearing means 27 described above, but now one bearing means 27 is arranged to support three hollow pieces 1 . According to an embodiment, one bearing means 27 may support at least two hollow pieces 1 . An advantage is that the efficiency of the simultaneously turning arrangement may be increased.

It will be apparent to a person skilled in the art that as technology advances, the basic idea of the invention may be implemented in many differ- ent ways. In some cases, features disclosed in this application may be used as such, irrespective of other features. On the other hand, when necessary, features disclosed in this application may be combined in order to provide various combinations. The invention and its embodiments are thus not restricted to the above-described examples provided for the sake of illustration, but the invention may vary within the scope of the claims.

Reference numerals

1 hollow piece

2 outer casing

3 inner space

4 gearbox

5 mechanical rectifier

6 toothed rim

7 power cable

8 body of hollow piece

9 generator

10 fin

1 1 support structure

12 mass piece

13 weight

14 rotating axle

15 pontoon

16 inner arrangement element

17 stabilizer fin

18 wire

19 control surface

20 support

21 toothed rail

22 turbine tube

23 bevelled section

24 auxiliary power unit

25 fin hinge

26 2 ^nd hollow piece

27 bearing means

28 directing surface

29 tank

30 pumping means

31 support axle

32 sun gear

33 planet gear

34 internal gear

35 auxiliary axle 36 seal

37 sealed space

100 arrangement

X common axis

W water

WB water base