WO2012103890A1

WO2012103890A1 - Wave power device

Info

Publication number: WO2012103890A1
Application number: PCT/DK2012/000011
Authority: WO
Inventors: Jan Olsen
Original assignee: JOLTECH ApS
Priority date: 2011-02-06
Filing date: 2012-02-03
Publication date: 2012-08-09
Also published as: DK201100073A

Abstract

A wave power device is disclosed for generating electrical power from waves, the device comprising a float (1) inside which is arranged a balanced gyroscopic rotor (6) with a shaft (20) providing a spin axis for said rotor (6), and a support structure (7, 8, 9, 10), for supporting said shaft (20) and providing for rotation of said rotor (6) and the shaft (20) about a second axis being perpendicular to the spin axis, wherein an electric machine (11) is arranged on the support structure (7, 8, 9, 10) to convert a spin of said shaft (20) into electric power.

Description

WAVE POWER DEVICE

The present invention relates to a device for generating electrical power from sea waves by utilizing a gyroscopic rotor.

BACKGROUND

Power generators driven by surface sea waves have been developed for many years in order to replace power plants utilizing combustion of fossil fuels or nuclear power plants and as an alternative to other renewable energy sources such as wind power generators.

A particular type of wave power devices comprises point absorbers which are moved by the wave motion to absorb energy from the wave motion. The difference in movement between the point absorber and a static or substantially static element may be used to produce power but the mechanical power transmitting coupling between the point absorber and the static element has shown to be a sensitive part of such wave power devices that is subject to excessive forces and requires regular maintenance. An example of such point absorber wave power device is found in US patent application No. 2006/0028026 Al . One alternative is gyroscopic wave power generators, where the motion of the point absorber drives a precession of the spin axis of a spinning rotor or flywheel suspended in a gimbal, and the precession drives a rotation of the gimbal axis at a frequency close to the wave motion frequency. An electric generator is coupled to the gimbal axis via a gearing as shown in US patent No. 7,003,947 and in European patent application No. 2 031 240 Al, where the point absorber of the latter is connected to a static element by means of a universal joint in order to utilize horizontal as well as vertical wave motion of the liquid.

The wave motion period is typically in the order of 5 to 10 seconds for surface waves of the sea and the rotational frequency of the gimbal axis will therefore be in the range of 0.1 to 0.2 Hz. In order to obtain an electric output from the generator at either a grid frequency of 50/60 Hz or at a frequency that is practically applicable to the rectifier of a frequency converter for converting into a grid frequency, i.e. at least around 10 Hz, an expensive multiple stage gearing between the gimbal axis and the electric generator is required with substantial transmission losses and which is susceptible to wear. Furthermore, such multistage gearing is heavy and will thus be disadvantageous to place in a point absorber.

It is an object of the present invention to provide an improved gyroscopic wave power generator.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

The present invention relates to a wave power device for generating electrical power from waves, the device comprising a float inside which is arranged a balanced gyroscopic rotor with a shaft providing a spin axis for said rotor, and a support structure for supporting said shaft and providing for rotation of said rotor and the shaft about a second axis being perpendicular to the spin axis, wherein an electric machine is arranged on the support structure to convert a spin of said shaft into electric power. By extracting the power generated by a precession of the spin axis for the rotor from the shaft which is rotating at a high speed the gearing of the rotating movement before coupling it to the rotor of the electric machine may be omitted or at least be of a much lower ratio that known for devices where the power is extracted from a gimbal shaft of the gyroscopic arrangement. Furthermore, the arrangement of the electric machine in mechanical contract with the shaft of the rotor allows for a preferred embodiment where the electric machine is arranged to be operated selectively as an electric motor to drive the spin of said shaft and as an electrical generator to convert a spin of said shaft into electric power. With such arrangement, the two separate functions of spinning the rotor at least during start-up of the device and for extracting power may be united in one electric machine which is a simpler and more cost efficient construction. The electric machine may in one preferred embodiment be an asynchronous machine, in which case a regenerative frequency converter may be provided for controlling the operation of the electric machine. Alternatively a brushless DC machine equipped with permanent magnets and driven by a four-quadrant motor controller, with the ability to regenerative braking, can be employed.

An emergency brake may furthermore be provided on the shaft of the rotor.

In a particularly preferred embodiment of the present invention, the rotation of the rotor and the shaft is coupled to the precession of the spin axis and thereby the rotor shaft in a power-transmitting arrangement so that the precession of the spin axis due to the action of the wave motion on the float will result in power being transmitted to the rotor for acceleration thereof during a start-up of the device or for the production of electric power by means of the electric machine. The coupling may be a mechanical coupling or alternatively a magnetic coupling.

In a preferred arrangement of the device, opposing parts of the shaft extend into an annular groove provided stationary with respect to the float, wherein the width of the groove exceeds the thickness of the parts of the shaft extending into the groove, so that the shaft may be in rolling contact with a side of the annular groove. A similar principle is applied, however for a completely different purpose, in the wrist exercise device known as a Dynabee, Powerball, Roller Ball or Dyna-Flex and is described in the US patent No. 3,726,146. When the float describes an elliptical or near circular movement due to the wave motion, the spin axis of the rotor will experience a precession which due to the spin of the rotor will result in rotation of the rotor and shaft about the second axis and create a torque normal to the spin axis which will force the parts of the shaft into engagement with the sides of the groove where they will roll. Hereby, the wave motion is directly linked to the spin of the rotor and power from the wave motion may be extracted from the rotation of the shaft by means of the electric machine. The groove being wider than the part of the shaft with which it is in engagement, such as an end part of the shaft or a wheel provided on the shaft, which means that the groove and the shaft are only engaging when the device is operating and mechanical wear of the device in non-operating time periods is thereby avoided together with damages during rough environmental conditions. It is advantageous that the parts of the shaft extending into the groove are provided with friction-enhancing means, such as a rubber compound to ensure the transfer of power between the groove's sides and the parts of the shaft in engagement with the sides of the groove. Alternatively, the parts of the shaft and the sides of the groove may be equipped with matching toothing.

It is preferred that said parts of the shaft extending into the groove are end parts of the shaft.

The support structure may in particular comprise a ring element which is arranged to rotate freely about said second axis. The ring element may comprise openings to receive opposing ends of the shaft so that the rotating movement of the shaft about the second axis is controlled by the openings of the ring element.

The ring element is preferably supported on the float by one or more tracks mounted stationary on the float by means of an elastic mounting element so that deformations of the float and/or the track or tracks may be absorbed by the elastic mounting element, such as a layer of a natural rubber or an artificial rubber composition, whereby excessive stresses between the float and the tracks are avoided. The support structure may further comprise a frame connected to said ring element and rotating with it, the frame having bearings for supporting the shaft on the frame, the shaft being supported so that it may turn due to a torque applied to the shaft about a third axis being perpendicular to the spin axis as well as the second axis, whereby the parts of the shaft extending into the groove comes into rolling contact with a side of the annular groove. The frame may in particular be of an elastic constitution, so that the shaft is substantially stationary with respect to the frame during operation of the device. The frame will thereby allow the shaft and rotor to turn with respect to the ring element due to the torque on the shaft caused by the precession thereof, so that the parts of the shaft come into engagement with the sides of the groove. The electric machine may advantageously be arranged on the frame so that the electric machine is stationary with respect to the shaft irrespective of the deformation of the frame due to the torque.

The device may further be equipped with support bearings are arranged on the ring element for supporting the ends of the shaft, the support bearings being displaceable in a direction parallel to the direction of the axis of rotation of the ring element, i.e. in a direction parallel to said second axis.

At least one actuator, such as an electric linear actuator may be provided to displace one end of the shaft in a direction parallel to the second axis for engaging the part of the shaft with the side of the annular groove. The actuator is preferably arranged on the ring element and its purpose is during start-up of the wave energy transforming arrangement to displace one end of the shaft in a direction parallel to the rotation axis of the ring element for engaging the end of the shaft with the side of the annular groove to ensure that the rotating movement of the ring element is transferred to a spin of the rotor. In a preferred embodiment, the actuator is arranged to act on one of the support bearings for displacement thereof and thereby displacement of the part of the shaft into engagement with the side of the annular groove. The float is preferably arranged on an arm connected to a substantially static arrangement by means of a joint, such as a universal joint, which allow for movement of the float in a horizontal direction as well as in a vertical direction. The arm is preferably connected to the static arrangement in a substantially non-rotational manner with respect to a longitudinal axis of the arm, and the device is preferably arranged so that the spin axis for the rotor is substantially perpendicularly to a longitudinal axis of the arm. The second axis is preferably substantially parallel to the longitudinal axis of the arm.

The static arrangement comprises preferably one or more pontoons, and a plurality of said floats, such as 4 to 20, preferably 6 to 16 floats may be connected to the same static arrangement.

Each of said floats is preferably provided with a drag-increasing plate extending substantially parallel to a longitudinal axis of the arm in order to ensure that the float will follow the horizontal movements of the wave motion as well as the vertical motion.

A restrictor may advantageously be provided on the static arrangement and having an opening through which the arm passes so as to restrict the movements of the arm. The opening in the restrictor is preferably of a substantially circular shape and the restrictor may furthermore be provided with a cushioning material at a rim of the opening, such as a natural or artificial rubber material.

A displacement arrangement may furthermore be provided to which the arm is connected so that the extent of the arm between the float and the restrictor may be adjusted by means of the displacement arrangement. Hereby, the magnitude of the amplitude of the movement of the arm may be adjusted to fit the magnitude of the wave motion of the liquid surface. The arm may also be provided with a section having an enlarged cross-sectional width, so that the displacement arrangement may displace the arm to a position, where the section of enlarged width will engage the opening of the restrictor and lock the movement of the arm. The device may furthermore be equipped with an electric energy source, such as an electric battery, for providing electric power to at least one control unit of the device. BRIEF DESCRIPTION OF FIGURES

A preferred embodiment of the present invention is shown in the accompanying drawing of which

Fig. 1 shows a float and an arm in perspective and partly sectioned view,

Fig. 2 is a cross-sectional view of a float,

Fig. 3 shows an embodiment of a wave energy plant provided with ten floats in a perspective view,

Fig. 4 is a diagram showing the principle of the displacement arrangement, and

Fig. 5 is a diagram of the electric part of the wave energy plant. DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION A float (1) for a wave power device and containing a wave energy transforming arrangement is shown in Fig. 1 together with an arm (4) connected to the float (1). The energy transforming arrangement comprises a balanced gyroscopic rotor (6) with a shaft (20) defining a spin axis of the rotor (6) and suspended in a torsional frame (7) by means of two main bearing assemblies (9). An asynchronous machine (11) which may be operated as an electric generator as well as an electric motor is mounted on the frame (7) so that the rotor shaft (20) passes through and directly drives the rotor of electric machine (11), i.e. no gearing is provided between the shaft (20) and the electric machine (11). An emergency brake (19) is also mounted on the frame (7) and is arranged to slow down and/or stop the rotation of the rotor shaft (20) e.g. in case the electric connection to the electric machine is disconnected. The frame (7) is suspended in a ring element (8) which is arranged rotatable about an axis that is an elongation of the longitudinal axis (5) of the arm (4) connected to the float (1). The ring element (8) is supported on twelve rolls (12) which engages with two tracks (13) connected to the inside of the float (1) by an elastic mounting element (32) and being static with respect to the float (1). The elastic mounting element (32) is provided to take up deformations of the float (1) and thereby avoid excessive stress between the tracks (13), the annular groove (22) and the float (1). On both ends of the shaft (20) of the rotor (6) are provided friction-enhancing means and those ends extend into an annular groove (22) provided on the inside of the float (1) and being static with respect to the float (1). In Fig. 1 the groove (22) is shown in the right hand part of the figure by partly cut-away of one of the tracks (13), groove (22), elastic mounting element (32) and part of the float (1), the cut-away being indicated by two punctuated lines. An actuator (27) is provided on the ring element (8) for during start-up of the wave energy transforming arrangement to displace one end of the shaft (20) in a direction parallel to the rotation axis of the ring element (8) for engaging the end of the shaft (8) with the side of the annular groove (22) to ensure that the rotating movement of the ring element (8) is transferred to a spin of the rotor (6). The electrical machine (1 1), which preferably is an asynchronous machine is connected to a junction box (15) containing a set of carbon brushes (16) for establishing electric contact with a corresponding set of slip rings (17) mounted electrically insulated on the inside of the float (1) for transferring electrical power to and from the electric machine (1 1). The set of slip rings (17) are via a cable (14, 18) through the arm (4) connected to a regenerative frequency converter (42).

The cross-section of the float (1) shown in Fig. 2 illustrates how the rotor (6) and the shaft (20) are suspended inside the float (1). The shaft (20) of the rotor (6) is suspended in two main bearing assemblies (9) with a set of main bearings (10) provided between the shaft (20) and the stationary main bearing assemblies (9) which is fixed to the frame (7). The main bearing assemblies (9) support the mass of the rotor (6) and the shaft (20) on the frame (7) and transfer the torque from the precession of the spin axis of the rotor (6) to the frame (7). The shaft (20) is furthermore supported on the ring element (8) by two support bearings (23), one near each end of the shaft (20). The support bearings (23) transfer the reaction force between the ends of the shaft (20) and the side of the groove (22) to the ring element (8). The support bearings (23) are mounted in bearing houses (24) on the ring element (8) so that they are allowed to move back and forth in the direction parallel to the axis of rotation of the ring element (8), herein also denoted the second axis, for providing for the ends of the shaft (20) to be in contact with one or the other side of the groove (20), depending on the direction of rotation of the ring element (8).

The float comprises two half parts (2a, 2b), a first half part (2a) wherein all the mechanical parts of the energy transforming arrangement are mounted and to which the arm (4) is secured, and a second half part (2b) that may be dismounted for allowing for access to the mechanical parts. The two half parts (2a, 2b) are assembled with an air and water proof flange joint (3). The half parts (2a, 2b) of the float may be manufactured in steel or aluminum, but a preferred material is a composite material made from a fiber material, such as glass fibers, in a matrix of a hardening artificial resin.

An embodiment of a wave energy plant is shown in Fig. 3 having ten floats (1) arranged on the opposing sides of a longitudinal pontoon (26) with five floats (1) on each side. Each float (1) is provided with a drag profile (43) to ensure that the horizontal movement of the water due to the wave motion is transferred to the float (1) as the present wave power device utilizes the horizontal movement as well as the vertical movement of the water due to the wave motion, and the vertical movement is transferred to the float (1) due to the buoyancy of the float (1) itself. The pontoon (26) is manufactured as an elongated steel tube which is closed off air and water proof at each end so that the pontoon (26) is air filled to provide the necessary buoyancy for the plant. Beneath the pontoon (26) is a concrete ballast block to position the plant low in the water. The pontoon (26) is anchored to the bottom of the see by means of anchor cables attached to one end (35) of the pontoon (26). For each of the floats (1) there is provided float attachment device on the pontoon (26) each having a displacement arrangement (31) which is connected to the arm (4) by means of a joint (30) which allows for movement of the arm (4) in the horizontal direction as well as in the vertical direction but prevents rotation of the arm (4). The joint could e.g. be a so-called universal joint or gimbal joint which is non-rotating around the longitudinal axis. The arm (4) passes through a restrictor (29) comprising a metal housing and an inner cushioning material (28) defining a circular opening through which the arm (4) passes. The displacement arrangement (31) may displace the joint (30) horizontally back and forth with respect to the opening in the restrictor (29) at a horizontal level above the center of the opening. Hereby, the displacement arrangement (31) can be applied to adjust the length of the arm (4) between the float (1) and the restrictor (29) opening according to the size of the waves so that the movement of the float (1) is as close to a circular movement, which is the most efficient pattern of movement for collecting energy from the waves. The horizontal difference between the joint (30) and the center of the opening in the restrictor (29) ensures that the float (1) will be at a lower average position at larger waves, which again is more efficient.

A section (25) of the arm (4) has an enlarged cross-sectional width, so that the displacement arrangement (31) may be employed for retracting the arm (4) to a safety position where the section (25) of enlarged width will engage the opening of the restrictor (29) and lock the movement of the arm (4), e.g. in case of environmental conditions that may harm the plant.

On the top of the pontoon (26) is for each two floats (1) arranged a control box (33) containing two independent control devices, one for each of the energy transformation devices for the two floats (1), which in the shown embodiment primarily is a regenerative frequency converter, i.e. a converter that may receive electrical power from the electric machine (1 1) at a varying frequency and convert it to a constant frequency power during ordinary operation of the plant and which during start-up of the plant may receive power from either an electrical battery (41) feeding power to a DC link of the frequency converter, an external source of AC or an internal source AC or DC source such as the power generating device of one of the floats (1) of the plant, which is activated for generating power for the start-up of the operation of the whole wave power plant. The control boxes (33) of the plant are mutually connected by means of a backbone cable (34) that comprises conductors for three phases as well as a null conductor, a ground conductor and a data transfer cable, such as a fiber optical cable for transmitting control data between the control boxes (33) and a central control unit (not shown) on shore. For smaller wave power plants close to the shore, the backbone cable (34) may be led to a station on shore whereas for larger wave power plants comprising a plurality of plants as the one shown and at a longer distance to the shore, it may be advantageous to provide a common high voltage AC or DC connection from the plant to the shore. Alternative embodiments of the energy transformation devices may be envisioned, such as a common DC link for all frequency converters or the use of DC electric machines (11) instead of the AC machines, preferably asynchronous machines. By the use of DC machines, the power electric part connecting the electric machine (1 1) to the DC link is omitted.

A preferred embodiment of the displacement arrangement (31) is shown in Fig. 4 comprising a double action hydraulic cylinder (36) where the two sides of the piston are connected hydraulically by means of a control valve (39) and a throttle valve (40) and parallel hereto by means of a pump (37) and a one-way valve (38). The piston may move back and forth slowly due to an external force on the arm (4) when the control valve (39) is open because the throttle valve (40) dampens the movement. When the control valve (39) is closed the displacement arrangement (31) will be locked on place. When the control valve (39) is closed and the pump (37) is activated, the piston will be displaced to the right on the figure to its extreme position and the enlarged section (25) of the arm (4) will engage the restrictor (29) and lock the arm (4) and the float (1) into a safe position. When the piston of the displacement arrangement (31) is moved back and forth the diameter of the circular movement allowed for the float (1) will be adjusted as discussed previously. A diagram of the electric system of the wave power plant is shown in Fig. 5. An asynchronous machine (1 1) which may operate as a motor as well as a generator is mechanically connected to the shaft (20) of the rotor (6). The asynchronous machine (1 1) is electric connected to a regenerative frequency converter (42) by means of a set of cables (14, 18) and power transferring device (16, 17) which can transmit the power across the rotating movement between the asynchronous machine (1 1) and the static arrangement of the pontoon (26) such as a set of carbon brushes (16) and slip rings (17). De regenerative frequency transformers (42) are on one side connected in parallel to a backbone cable (34) for transmitting power on shore. In the shown embodiment, one of the wave power devices may be employed to start-up of the plant by connecting an electrical battery (41) to the DC link of the frequency converter so that the electric machine (1 1) may be operated as a motor to spin the rotor (6) and thereby initiate the generation of power from that float (1) to start-up of the remaining part of the plant.

In the operation of the wave power device the following operating modes may be employed: a) A deactivated operational mode where the rotor (6) is at a stand-still which means that the wave power device is inactive and there is no wear on the rotating components. b) A start-up operational mode where the rotor (6) by means of the electric machine (1 1) operating as a motor is rotated. When the float (1) describes a circular movement due to the wave motion, the spin axis of the rotor (6) will experience a precession, which together with the spin of the rotor (6) will result in a torque that will cause the ring element (8) to rotate back and forth with increasing amplitude. When the amplitude excesses half a turn the ring element (8) will continue to rotate in one or the other direction with a speed coupled to the frequency of the wave motion. The direction of the rotation of the ring element (8) is random and is without importance for the operation of the wave power device. However, in case the actuator (27) is provided in the device and is employed in the start-up operational mode, the direction of rotation of the ring element (8) is predetermined. With increasing rotational speed of the ring element (8) will the torque generated by the precession of the rotor (6) also increase in magnitude with the result that the rotor (6) and its shaft (20) will turn more and more relatively to the ring element (8) because the frame (7) by means of which the shaft (20) is connected to the ring element (8) is elastic. At a certain point, the ends of the shaft (20) will come into contact with the sides of the annular groove (22) and the friction-enhancing means (21) on the shaft (20) will engage the side of the groove (22). In the beginning, the engagement between the shaft (20) ends and the groove (22) sides will be a slipping contact which will cause the shaft (20) and the rotor (6) to accelerate until the rotational speed is equal to the rotational speed of the ring element (8) multiplied with the ratio between the diameter of the annular groove and the diameter of the part of the shaft (20) including the friction-enhancing means (21) engaging the groove (22). The energy necessary to accelerate the rotor (6) comes from the wave motion driving the rotation of the ring element (8). The spin of the rotor (6) is now coupled directly to the wave motion of the surface of the liquid.

By start-up of a whole wave power plant comprising a plurality of floats (1) including wave power devices it may be advantageous that at least one of the wave power device may be started up by means of an internal energy source, such as an electrical battery (1 1) and that the start-up of the remaining wave power devices of the whole plant subsequently is powered by the one or more wave power devices that were initially started up by means of the internal energy source or sources. Hereby, the whole wave power plant may perform a start-up operation as a stand-alone unit without the need for external power. c) A stand-by operational mode where the rotor (6) is coupled directly to the wave motion of the surface of the liquid but does not absorb energy from the wave motion. The float (1) with the wave power device and the arm (4) appears in this operational mode as an undamped mechanical oscillating system of a high Q factor, which is in resonance and in phase with the wave motion at the liquid surface. The wave period of ordinary wind generated sea waves is generally in the range of 5 to 10 seconds so the frequency of the rotation of the ring element (8) will in this operational mode be of the order of 0.1 to 0.2 Hz. The Q factor is for resonators defined in terms of the ratio of the energy stored in the resonator to the energy supplied by a generator, per cycle, to keep the signal amplitude constant. For high Q factors, the factor equals the ratio of the resonant frequency to the bandwidth of the resonator. When the electric machine (11) in the stand-by operational mode is activated as generator and thus affects the shaft (20) of the rotor (6) with a braking torque, the wave power device starts to absorb energy from the wave motion of the surface of the liquid and provide the absorbed energy as electric power to e.g. an electric grid. The activation of the electric machine (11) may be rapid or gradually according to the present requirements, the connection of a larger wave power plant to the public power grid may require a certain period of time to avoid disturbances on the grid. d) An energy absorption operational mode where the rotor (6) is coupled directly to the wave motion of the surface of the liquid and absorbs energy from the wave motion. The float (1) with the wave power device and the arm (4) appears in this operational mode as a damped mechanical oscillating system of a low Q factor, which is in resonance but out of phase with the wave motion at the liquid surface. The electric machine (11) is in this operational mode affecting the shaft (20) with a constant braking torque and the angular velocity the spinning rotor (6) will be substantially constant, and the electric power provided from the electric machine (1 1) is substantially constant during the whole period of the wave motion at the liquid surface. e) An energy providing operational mode, where the rotor (6) is coupled directly to the wave motion of the surface of the liquid and provides energy to the wave motion. The electric machine (11) will in this operational mode operate as an electric motor that affects the rotor (6) shaft (20) with an accelerating torque. This operational mode is advantageous during test operation of a wave power plant so that energy absorbed by means of some of the floats (1) of the plant may be transferred to other floats (1) of the same plant and be provided back to the liquid, whereby the plant as a whole does not need to be connected to the electric grid during test operation of the plant. The size of the floats (1) in a wave power plant should be adapted to the predominant wave height at the location of the plant. A typical diameter is in the range of 1.5 meter to 5 meters with a maximum absorption in the range of 5 kW to 250 kW per float (1). However, smaller as well as larger floats (1) may be envisioned within the scope of the present invention.

LIST OF REFERENCES

1 Float

2a First half part of float

2b Second half part of float

3 Flange joint

4 Arm

5 Longitudinal axis of arm

6 Gyroscopic rotor

7 Frame

8 Ring element

9 Main bearing assemblies

10 Main bearings

1 1 Electric machine

12 Rolls

13 Tracks

14 Cable

15 Junction box

16 Carbon brushes

17 Slip rings

18 Cable 19 Emergency brake

20 Shaft of rotor

21 Friction-enhancing means on shaft

22 Annular groove

23 Support bearings

24 Support bearing houses

25 Arm section with enlarged cross-sectional width

26 Static arrangement, pontoon

27 Actuator

28 Cushioning material

29 Restrictor

30 Joint

31 Displacement arrangement

32 Elastic mounting element

33 Control box

34 Backbone cable

35 One end of pontoon

36 Hydraulic cylinder

37 Pump

38 One-way valve

39 Control valve

40 Throttle valve

41 Electric battery ,

42 Regenerative frequency converter

43 Drag profile

Claims

1. A wave power device for generating electrical power from waves, the device comprising a float (1) inside which is arranged

a balanced gyroscopic rotor (6) with a shaft (20) providing a spin axis for said rotor (6), and

a support structure (7, 8, 9, 10), for supporting said shaft (20) and providing for rotation of said rotor (6) and the shaft (20) about a second axis being perpendicular to the spin axis,

wherein an electric machine (11) is arranged on the support structure (7, 8, 9, 10) to convert a spin of said shaft (20) into electric power.

2. A device according to claim 1, wherein the electric machine is arranged to be operated selectively as an electric motor to drive the spin of said shaft (20) and as an electrical generator to convert a spin of said shaft (20) into electric power.

3. A device according to claim 1 or 2, comprising a power-transmitting arrangement by means of which the rotation of the rotor (6) and the shaft (20) is coupled to the precession of the spin axis.

4. A device according to claim 3, wherein the power-transmitting arrangement comprises an annular groove (22) provided stationary with respect to the float (1), where opposing parts of the shaft (20) extend into the groove (22) and wherein the width of the groove (22) exceeds the thickness of the parts of the shaft (20) extending into the groove (22), so that the shaft (20) may be in rolling contact with a side of the annular groove (22).

5. A device according to claim 4, wherein the parts of the shaft (20) extending into the groove (22) are provided with friction-enhancing means (21).

6. A device according to claim 4 or 5, wherein said parts of the shaft (20) extending into the groove (22) are end parts of the shaft (20).

7. A device according to any of claims 3 to 6, wherein the support structure (7, 8, 9, 10) comprises a ring element (8) which is arranged to rotate freely about said second axis.

8. A device according to claim 7, wherein the ring element (8) is supported on the float (1) by one or more tracks (13) mounted stationary on the float (1) by means of an elastic mounting element (32).

9. A device according to claim 7 or 8, wherein the ring element (8) comprises openings to receive opposing ends of the shaft (20). 10. A device according to any of claims 7 to 9, wherein the support structure further comprises a frame (7) connected to said ring element (8) and rotating with it, the frame (7) having main bearings (9,

10) for supporting the shaft (20) on the frame (7), the shaft (20) being supported so that it may turn due to a torque applied to the shaft (20) about a third axis being perpendicular to the spin axis as well as the second axis, whereby the parts of the shaft extending into the groove (22) comes into rolling contact with a side of the annular groove (22).

11. A device according to claim 10, wherein the frame (7) is of an elastic constitution, so that the shaft (20) is substantially stationary with respect to the frame (7) during operation of the device.

12. A device according to claim 10 or 11, wherein the electric machine (11) is arranged on the frame (7).

13. A device according to any of claims 9 to 12, wherein support bearings (23) are arranged on the ring element (8) for supporting the ends of the shaft (20), the support bearings (23) being displaceable in a direction parallel to the direction of the axis of rotation of the ring element (8), i.e. in a direction parallel to said second axis.

14. A device according to any of claims 4 to 13, wherein at least one actuator (27) is provided to displace one end of the shaft (20) in a direction parallel to the second axis for engaging the part of the shaft (8) with the side of the annular groove (22).

15. A device according to claim 14, wherein the actuator (27) is arranged to act on one of the support bearings (23) for displacement thereof.

16. A device according to any of the preceding claims, wherein the float (1) is arranged on an arm (4) connected to a substantially static arrangement (26) by means of a joint (30), which allow for movement of the float (1) in a horizontal direction as well as in a vertical direction.

17. A device according to claim 16, wherein the arm (4) is connected to the static arrangement (26) in a substantially non-rotational manner with respect to a longitudinal axis (5) of the arm (4).

18. A device according to claim 16 or 17, wherein the spin axis for the rotor (6) is substantially perpendicularly to a longitudinal axis (5) of the arm (4).

19. A device according to claim 18, wherein said second axis is substantially parallel to the longitudinal axis (5) of the arm (4).

20. A device according to any of claims 16 to 19, wherein the static arrangement (26) comprises one or more pontoons (26).

21. A device according to any of claims 16 to 20, wherein a plurality of said floats (1), such as 4 to 20, preferably 6 to 16 floats (1) are connected to the same static arrangement (26).

22. A device according to any of claims 16 to 21, wherein each of said floats (1) is provided with a drag-increasing plate (43) extending substantially parallel to a longitudinal axis (5) of the arm (4).

23. A device according to any of the preceding claims, wherein an emergency brake (19) is provided on the shaft (20) of the rotor (6).

24. A device according to any of claims 16 to 23, wherein a restrictor (29) is provided on the static arrangement (26) and having an opening through which the arm (4) passes so as to restrict the movements of the arm (4).

25. A device according to claim 24, wherein the opening in the restrictor (29) is of a substantially circular shape.

26. A device according to claim 24 or 25, wherein the restrictor (29) is provided with a cushioning material (28) at a rim of the opening.

27. A device according to any of claims 24 to 26, wherein a displacement arrangement (31) is provided to which the arm (4) is connected so that the extend of the arm (4) between the float (1) and the restrictor (29) may be adjusted by means of the displacement arrangement (31).

28. A device according to claim 27, wherein the arm (4) is provided with a section (25) having an enlarged cross-sectional width, so that the displacement arrangement

(31) may displace the arm (4) to a position, where the section (25) of enlarged width will engage the opening of the restrictor (29) and lock the movement of the arm (4).

29. A device according to any of the preceding claims, wherein the electric machine (11) is an asynchronous machine.

30. A device according to any of the preceding claims, wherein a regenerative frequency converter (42) is provided for controlling the operation of the electric machine (11).

31. A device according to any of the preceding claims comprising an electric energy source, such as an electric battery (41), for providing electric power to at least one control unit of the device.