GB2480337A

GB2480337A - Wave energy converter with an orientating mechanism

Info

Publication number: GB2480337A
Application number: GB1012162A
Authority: GB
Inventors: William Dick; Carlos Villegas
Original assignee: Wavebob Ltd
Current assignee: Wavebob Ltd
Priority date: 2010-05-13
Filing date: 2010-05-13
Publication date: 2011-11-16
Anticipated expiration: 2030-05-13
Also published as: GB2480337B; GB2492669A; GB201212838D0; GB201012162D0; GB2492669B

Abstract

A wave energy converter 400 comprising a wave energy absorber 105 for absorbing wave energy, a power take off (PTO) 405 coupled to the wave absorber for harnessing wave energy and an orientating mechanism for adjusting the orientation of the PTO in response to changes in the orientation of the wave energy absorber. Preferably the PTO comprises a rack and pinion system including a pair of pinions 425a, 425b located on opposite sides of the rack 422 and each connected to a generator 426a, 426b. The wave absorber may include a float, inside which the orientating mechanism is located. Preferably the orienting mechanism is a gimbal and the wave energy absorber is a point absorber which may include a further outer torus float to define a two body oscillator.

Description

A wave energy converter

Field of the Invention

The present invention relates to a wave energy converter. In particular the present invention relates to a wave energy converter which includes an adjustable orientating mechanism for adjusting the orientation of the PTO in response to changes in the orientation of the wave energy absorber.

Background

Wave energy converters (WEC) are known in the art. Examples of such systems include those described in patents EP1439306, EP1 295031 and EP1036274 of which the present applicant is the proprietor. Such WEC5 are usefully deployed in a maritime environment and generate useful power from wave motion. Typically, WEC5 employ a wave energy absorber operably coupled to a power take (PTO). The wave energy absorber drives the PTO to produce energy which is then converted into electrical energy. In periods of large swells the forces experienced by WEC5 from passing waves is vast often causing the WEC5 to sway vigorously. PTO5 are often damaged as result of the vigorous movement of the WEC due to misalignment, buckling or other types of mechanical failure.

There is therefore a need for a wave energy converter which addresses at

least some of the drawbacks of the prior art.

Sum mary These and other problems are addressed by providing a wave energy converter which includes an adjustable orientating mechanism for adjusting the orientation of the PTO in response to changes in the orientation of the wave energy absorber.

Accordingly, a first embodiment provides a wave energy converter as detailed in claim 1. Another embodiment relates to a wave energy conversion system as detailed in claim 38. The invention also relates to a wave en Advantageous embodiments are provided in the dependent claims.

These and other features will be better understood with reference to the followings Figures which are provided to assist in an understanding of the teaching of the application.

Brief Description Of The Drawings

The present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a wave energy converter.

Figure 2 is a diagrammatic view of a wave energy absorber for operably coupling to the wave energy converter of Figure 1.

Figure 3 is a diagrammatic view of details of the wave energy converter of Figure 1.

Figure 4 is a diagrammatic view of details of the wave energy converter of Figure 1.

Figure 5 is a diagrammatic view of details of the wave energy converter of Figure 1.

Figure 6 is a diagrammatic view of details of the wave energy converter of Figure 1.

Detailed Description Of The Drawings

The invention will now be described with reference to an exemplary wave energy converter which is provided to assist in an understanding of the teaching of the invention.

Referring to the drawings there is illustrated an exemplary wave energy converter (WEC) 400 for harnessing wave energy. The WEC 400 comprises a power take-off (PTO) 405 operably coupled to a wave energy absorber 105.

Before describing specifics of the PTO 405 aspects of the wave energy absorber 105 will first be described. It will be understood that wave energy absorbers are known in the art, an example of which is shown in European Patent no. 1,295,031 of which the present applicant is the proprietor and replicated in Figure 2 of the instant application. This exemplary wave energy absorber 105 comprises at least two devices (floats) 110, 111 which define a two body oscillator. The wave energy absorber 105 may be classified as a point absorber. However, it is not intended to limit the teaching of the present invention to a specific type of wave energy absorber. Point absorbers are usually axi-sym metric about a vertical axis, and by definition their dimensions are small with respect to the wavelength of the predominant wave. The devices usually operate in a vertical mode, often referred to as heave'. Typically, a surface piercing float rises and falls with the passing waves and reacts against the seabed or a taut mooring. As such they are capable of absorbing energy arising from changes in the surface level rather than from forward motion of breaking seas. The theoretical limit for the energy that can be absorbed by a single isolated, heaving, axi-symmetrical point absorber has been shown to depend on the wavelength of the incident waves rather than the cross sectional area of the device, i.e. from the wavelength divided by 2.Thus the wavelength is a critically important criterion, resulting in the attraction of locating the point absorber devices well outside the region of breaking waves, and where they will be open to long wavelength ocean swell or heave'.

In the exemplary wave energy absorber 105, each of the two devices comprises a surface float and/or at least one submerged wave driven body 115 below the surface of the body of liquid. The outer surface float 111 provides an annular torus which surrounds the inner surface float 110. Power take off linkages 139 are provided between the inner surface float 110 and the outer torus 111. By configuring each of the two devices 110, 111 to oscillate at different frequencies relative to one another in response to passing waves, relative movement between the at least two devices 110, 111 may be used to generate an energy transfer which may be harnessed by the linkages 139 between the at least two devices 110, 111. The linkages are coupled to the PTO 405 which harnesses the mechanical energy generated by the wave energy absorber 105. The PTO 405 is operable to convert linear motion into rotary motion which is then converted into electrical energy. The PTO 405 comprises a translating mechanism in the form of an elongated rack 422 which operably drives a pair of pinions 425a, 425b which in turn drive corresponding generator 426a, 426b. In the exemplary arrangement two motors 426 are provided but it will be appreciated that the present teaching is not to be construed as limited to such an exemplary arrangement. The inner float 110 of the wave absorber 105 defines a hollow interior volume 409 in which the PTO 405 is housed. In this example, the float 110 includes a central cylindrical portion 412 which terminates at one end thereof with a frustoconical portion 415 and the opposite end with a dome portion 420.

The rack 422 is operably coupled to the power take off linkages 139 that harness power as result of the inner float 110 and the torus 111 oscillating at different frequencies in response to passing waves. A translator 428 which forms part of the power take off linkages 139 reciprocates in response to the oscillations. Reciprocal movement of the translator 428 causes the rack 422 to reciprocate in tandem. The pin ions 425a, 425b operably engage respective opposite sides of the rack 422 and rotate in response to the longitudinal motion generated by the rack 422 reciprocating. The rack 422 extends through an aperture 430 formed on the inner float 110 such that a first portion of the translator 428 is located in the interior volume 409 and a second portion of the translator 428 is located externally of the interior volume 409. A seal 434 prevents sea water from entering the interior volume 409 while allowing the translator 428 to move axially through the aperture 430. The translator 428 defines a longitudinal axis 435 which is substantially co-axial with the longitudinal axis of the rack 422. Each pinion 425a, 425b and its associated generator 426 share a drive shaft 440 that defines a common axis of rotation 445. The common axis of rotation 445 is substantially perpendicular to the longitudinal axis 435.

The longitudinal axis of the rack 422 is aligned coaxially with the heave axis of the wave absorber 102. The rack 422 provides a plurality of individual teeth which are engageable with the pin ions 425 SO as to translate and transfer linear motion along the heave axis to rotational motion necessary for actuation of the motors 426. In the exemplary arrangement shown two separate pin ions 425a, 425b are each coupled to the same rack 422-albeit to different surfaces, each of the difference surfaces comprising a set of teeth that are individually engageable with corresponding teeth on the pinions 425.

The rotary generator(s) 426 are mounted on an adjustable orientating mechanism which is operable for adjusting the orientation of the PTO 405 in response to changes in the orientation of the wave energy absorber 105. In other words, the orientating mechanism dynamically tracks the orientation of a wave energy absorber 105. In the exemplary embodiment the orientating mechanism comprises a supporting member 455 that is pivotably mounted within the interior volume 409 of the inner float 110. It is not intended to limit the teaching of the present invention to a specific type of orienting mechanism.

Alternative orientating mechanisms such as a gimbal may be usefully employed for adjusting the orientation of the PTO 405. The supporting member 455 is rotatable relative to the longitudinal axis of the rack 422. In an optimum arrangement, a major surface 460 of the supporting member 455 on which the generators 426 are mounted is dynamically oriented to be at right angles to longitudinal axis of the rack 422. A portion of the rack 422 extends through a segment of box section 463. The box section 463 accommodates the pin ions 425 therein so that their teeth mesh with the teeth on the rack 422. The box section 463 is mechanically arranged relative to the rack 422 so that it sways in tandem with the rack 422. In other words, if the rack 422 moves back and forth, the box section 463 also moves back and forth. However, it will be appreciated that the box section 463 does not reciprocate axially. A shaft 470 extends outwardly from the box section 463 to an annular member 472 and defines an axis of rotation on which the circular supporting member 455 pivots. The diameter of the annular member 472 is greater than the diameter of the supporting member 455 to allow the supporting member 455 to pivot in response to the rack 422 swaying from side to side. If the torus 111 and the inner float 110 are not aligned along the heave axis it may cause the rack 422 to sway. The moveable supporting member 455 is designed to track the orientation of the rack 422 as it sways so the surface 460 is substantially perpendicular with the longitudinal axis of the rack 422. The orientation of the supporting member 455 inherently tracks changes in the orientation of the wave energy absorber 105. Such an arrangement greatly improves the overall sea worthiness of the WEC 400 and significantly reduces the need for constraints to maintain alignment between the torus 111 and inner float 110.

The WEC 400 has many advantages. The diameters of the pin ions 425 and the rotors of the generators 426 can be suitably sized to maximize the generation of rotary motion. Velocities are increased in proportion to the ratio of the diameters of the generators 426 and the pinions 425. It will be appreciated that some of the potential for increased velocity may usefully be offset by a reduction in stroke length. One of the primary advantages is that the generators 426 are not in direct contact with the wave energy absorber 105 as the rack and pinion arrangement is operably coupled there between. The mechanical tolerances of the rack and pinion arrangement is significantly greater than those of the generators 426. Thus the rack and pinion arrangement is more robust than the generators 426. As a consequence, the rack and pinion arrangement is much better suited to coping with the translator 428 rocking from side to side as it reciprocates compared to the drive shafts 440 of the generators 426. As the translator 428 moves it may not travel along the exact same longitudinal path as the oscillating floats 110, 111 may cause it to sway. A major problem associated with wave energy converters where the power is recovered from the relative movement between two or more large oscillating bodies is the need to maintain the oscillating bodies in close alignment along the heave axis. This is especially important where the prime mover in the power take off is a hydraulic ram or a linear generator with one part attached to the torus (eg the stator) and the other to the float (eg the translating member). The orienting mechanism of the present application significantly reduces the risk that components of the PTO become misaligned, buckled or experience mechanical failure as result of non-symmetrical movement of the WEC 400.

It will be understood that what has been described herein are exemplary embodiments of a wave energy converter 400 and a wave energy conversion system incorporating the converter 400. While the present invention has been described with reference to an exemplary arrangement it will be understood that it is not intended to limit the teaching of the present invention to such arrangements as modifications can be made without departing from the spirit and scope of the present invention.

The words comprises/comprising when used in this specification are to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Claims

Claims 1. A wave energy converter comprising: a wave energy absorber for absorbing wave energy, a power take off (PTO) operably coupled to the wave absorber for harnessing wave energy, and an orientating mechanism for adjusting the orientation of the PTO in response to changes in the orientation of the wave energy absorber.
2. A converter as claimed in claim 1, wherein the PTO comprises an elongated rack.
3. A converter as claimed in claim 2, wherein the PTO further comprises at least one pinion configured to operably engage the rack such that reciprocal movement of the rack drives the at least one pinion.
4. A converter as claimed in claim 3, wherein the at least one pinion is operably coupled to an associated rotary motor such that rotary movement of the at least one pinion drives the motor.
5. A converter as claimed in claim 4, wherein a pair of pinions are provided each associated with a corresponding rotary motor.
6. A converter as claimed in claim 5, wherein each pinion operably engages a respective opposite side of the rack.
7. A converter as claimed in any one of claims 3 to 6, wherein the rack and the individual pinion each have teeth which operably mesh.
8. A converter as claimed in any one of claims 4 to 7, wherein the wave absorber comprises a float.
9. A converter as claimed in claim 8, wherein the float defines a volume for accommodating the orienting mechanism therein.
10. A converter as claimed in claim 8 or 9, wherein the orienting mechanism comprises a supporting member.
11. A converter as claimed in claim 10, wherein the supporting member defines a planar supporting surface.
12. A converter as claimed in claim 10 or 11, wherein the supporting member is pivotably mounted.
13. A converter as claimed in claim 12, wherein the supporting member is mounted on a shaft.
14. A converter as claimed in claim 13, wherein the shaft defines an axis of rotation about which the supporting member is rotatable.
15. A converter as claimed in claim 14, wherein a segment of box section surrounds a portion of the rack.
16. A converter as claimed in claim 15, wherein the shaft is operably coupled to the box section.
17. A converter as claimed in claim 16, wherein the box section is rotatable about the axis of rotation.
18. A converter as claimed in claim 16 or 17, wherein the box section and the supporting member are rotatable in tandem.
19. A converter as claimed in any one of claims 10 tol 8, wherein the rack extends through an aperture formed on the supporting member.
20. A converter as claimed in any one of claims 9 to 19, wherein the volume is sealed for preventing water entering the volume.
21. A converter as claimed in any one of claims 10 to 20, wherein each rotary motor is mounted on the supporting member.
22. A converter as claimed in any one of claims 8 to 21, wherein the float comprises a central cylindrical portion.
23. A converter as claimed in claim 22, wherein the central cylindrical portion terminates at one end thereof in a frustoconical portion.
24. A converter as claimed in claim 23, wherein the central cylindrical portion terminates at the other end thereof in a dome portion.
25. A converter as claimed in any one of claims 8 to 24, wherein the wave absorber further comprises an outer torus which surrounds the float such that the torus and float define a two body oscillator.
26. A converter as claimed in claim 25, wherein the wave absorber further comprises power take off linkages operably coupled to the two body oscillator.
27. A converter as claimed in claim 26, wherein the linkages comprise a translator operably coupled to the rack for driving thereof.
28. A converter as claimed in claim 27, wherein the translator defines a longitudinal axis which is substantially co-axial with a longitudinal axis of the rack.
29. A converter as claimed in claim 27 or 28, wherein the translator is dimensioned such that a first portion of the translator is located in the volume and a second portion of the translator is located externally of the volume.
30. A converter as claimed in claim 29, wherein the translator extends through an aperture formed on the float.
31. A converter as claimed in claim 30, wherein the float comprises a sealing arrangement for sealing the aperture.
32. A converter as claimed in claim 31, wherein the sealing arrangement accommodates axial movement of the translator through the aperture.
33. A converter as claimed in any one of claims 10 to 19, wherein the supporting member is moveable for adjusting the orientation of a major surface thereof relative to a longitudinal axis of the rack.
34. A converter as claimed in claim 33, wherein the supporting member is pivotable for adjusting the orientation of a major surface thereof perpendicular with the longitudinal axis of the rack.
35. A converter as claimed in any one of claims 1 to 34, wherein the supporting mechanism comprises a gimbal.
36. A converter as claimed in any one of claims 1 to 35, wherein the wave energy absorber is a point absorber.
37. A converter substantially as described hereinbefore with reference to the accompanying Figures.
38. A wave energy conversion system comprising the converter as claimed in any one of claims 1 to 36.