Title of Invention

WAVE POWER APPARATUS WITH LINKAGE UNIT AND A METHOD OF EXTRACTING POWER FROM WAVES

Abstract

Wave power apparatus comprising a plurality of buoyant elongate body members, at least one adjacent pair of body members being interconnected I by "a linkage unit to form an articulated chain, each body member of said I pair being connected to the respective linkage unit by linkage means (31) permitting relative rotation of the body members; power extraction means (42) adapted to resist and extract power from the relative rotation, the power extraction means (42) being located substantially within each linkage unit; and wherein each linkage unit (30) is arranged to permit relative rotation between the linkage unit (30) and a first body member about a first axis of rotation only at a first end of the linkage unit (30), and to permit relative rotation between the linkage unit (30) and a second body member (6) about a second axis of rotation only at a second end of the linkage unit (30); wherein the first and second axes of rotation are mutually orthogonal.

Full Text

Wave Power Apparatus This invention relates to a linkage unit, apparatus and method, for extracting power from water waves, particularly ocean waves. Ocean waves represent a significant energy resource. It is known to use a wave energy converter to extract power from such waves. An improved apparatus is shown in our WO 00/17519. This shows apparatus for extracting power from ocean waves comprising a number of buoyant cylinder body members connected together at their ends to form an articulated chain-like structure. Each pair of adjacent cylindrical members is directly connected together by coupling members which permit relative rotation of the cylindrical members about at least one axis. Preferably, adjacent coupling members permit relative rotation about mutually orthogonal transverse axes. Preferably each body member has one or more end caps with corresponding linkage means to marry with the linkage means of the linkage unit. Preferably the linkage unit is arranged to permit relative rotation between the linkage unit and a first body member about a first axis of rotation at a first end of the linkage unit, and to permit relative rotation between the linkage unit and a second body member about a second axis of rotation at a second end of the linkage unit. Preferably the power extraction means includes a hydraulic ram assembly. Preferably the hydraulic ram assembly comprises a plurality of rams. Preferably the power extraction means includes a hydraulic ram assembly fox each axis of rotation. Preferably the power extraction means includes two hydraulic ram assemblies acting about each axis of rotation. Preferably the end caps have a number of cavities to receive respective ends of the power extraction means. Preferably the power extraction means has at least one seal, such as a bellows or diaphragm seal, to to be resonant in small waves to increase power capture and which may be set in large waves to limit power absorption and maximise survivability. Preferably the apparatus includes one or more of a ballasting system, mooring system, and means to apply a roll bias angle to the axes of rotation. Preferably the linkage unit includes access means, such as one or more hatches, to allow inspection, repair and maintenance on or off site. The power extraction means may be integral with, linked to or separate from the linkage means. In one embodiment of the present invention, separate linkage means are provided for the movement about each axis. Each linkage means may be independent, or may be linked to other linkage means. The nature of the buoyant body members may correspond with the description of said members in WO 0 0/17519, which is included herein by way of reference. That is, said body members are preferably substantially elongate, cylindrical, and will form a chain-like structure. The apparatus preferably has a length of the same order of magnitude as the longest wavelength of the waves from which power is extracted, and may be free to adopt an equilibrium position with respect to any instantaneous wave pattern. wherein the ballasting system varies the roll bias angle of the chain-like structure. According to a second aspect of the present invention, thei~e is provided a linkage unit for use in the apparatus of claim 1, comprising: linkage means for interconnection between the body members permitting relative rotation at either end of the unit; power extraction means adapted to resist and extract power from the relative rotation of the body members ; the power extraction means being located substantially within the linkage unit. Preferably the linkage unit is arranged to permit relative rotation between the linkage unit and a first body member about a first axis of rotation at a first end of the linkage unit, and to permit relative rotation between the linkage unit and a second body member about a second axis of rotation at a second end of the linkage unit. Preferably the power extraction means includes a hydraulic ram assembly. Preferably the hydraulic ram assembly comprises a plurality of rams. extraction means from one or both axes o£ rotation, such that when the apparatus is operating at partial capacity, the one or more power extraction means is connected solely to the first or second power generation means. Preferably constraint is applied to each power extraction means of the linkage unit in order to induce a cross-coupled response which may be tuned to be resonant in small waves to increase power capture and which may be set in large waves to limit power absorption and maximise survivability. Preferably the linkage unit includes access means, such as one or more hatches, to allow inspection, repair and maintenance on site. According to a third aspect of the present invention, there is provided a method of extracting power from waves comprising the steps of: deploying an apparatus as described in the first aspect of the present invention; orientating the structure such that a front end of the structure faces into the oncoming waves; and extracting the power absorbed in the or each linkage unit. Preferably the method can be carried out close to site, on site or in situ, because the linkage unit(s) can be fully assembled, analysed and tested, for example on a test rig, relating to its power extraction prior to its installation and use. Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figures la and lb show overall plan and side views of apparatus of the present invention; Figure 2 shows a perspective view of part of prior art apparatus according to the one embodiment of the invention shown in WO 00/17519 for directly linking body members; Figure 3 shows front and inside detail of one part of Figure 2; Figure 4 shows a schematic line drawing of the conjunction in Figures 2 and 3; Figure 5 shows a detail of the apparatus in Figure 1 illustrating a linkage unit of the present invention; Figures 6, 7 and 12 show different external and part-internal views of the linkage unit in Figure 5; emergence in large waves (as is discussed in our WO 00/17519). That is, the overall chain-like structure of the apparatus 2 may be configured to encourage hydrostatic clipping in extreme conditions. The body members 4, 6, 8 and 10 may be provided with fins, bilge keels or other protrusions to add hydrodynamic damping to any direction of motion desired. The front body member 4 is provided with a streamlined (for example conical) front end to minimise drag in extreme seas, whilst the rear body member 10 has a flat rear end to increase damping along the axis of the chain structure to add damping to the mooring response. The body members 4, 6, 8, 10 may be formed from any suitable material. Concrete is one suitable material, although steel or fibreglass are also useable. The body members 4, 6, 8, 10 are preferably ballasted to float with its centre line on or near the water-plane (approximately 50% displacement by volume) . The body members 4, 6, 8, 10 could include an active or passive ballasting system, which varies the level at which the individual body members or the complete apparatus floats. If incorporated, the ballasted system may be capable of being disabled and/or removed. The ballasting system hastens the onset of hydrostatic clipping in extreme seas, thus helping to minimise the maximum loads and bending Furthermore, each ram-housing compartment 2 0 requires its own power generation means or components and connected hydraulic systems, and must he separately tested prior to installation and use. Such testing may or may not be in conjunction with the main part of the body members 12, being 27 meters long. Also, in the event of failure of the linkage or joint hydraulic system, restraint on the joint may be lost, possibly leading to further damage or failure. Whilst it is possible to provide independent systems in this arrangement for each of the individual restraint means acting about a particular axis of rotation, it is not economic to do so. As shown in Figures 1,5, 6 et al, the present invention provides a linkage unit 3 0 for interconnection between a plurality of adjacent buoyant body members 4, 6, 8, 10. Each adjacent pair of body members 4, 6, 8, 10 is interconnected by a linkage unit to form an articulated chain, consecutively arranged. The linkage unit 3 0 comprises linkage means 31 to conjoin the unit 3 0 with the respective ends of each adjacent pair of body members 4, 6, 8, 10 to permit relative movement of said body members 4, 6, 8, 10 about two axes of rotation. The linkage unit 3 0 may be of any shape and size determined by the annual wave climate of the locality in which it is used, and by the weather conditions it is likely to encounter, i.e. the shape etc., within the body members 4, 6, 8, 10- The linkage bearings 32, 36 may be provided with external seals 41 to allow the bearings and pins 34 to be accessed for inspection, maintenance or repair insitu or near-site without water ingress into the linkage unit and/or body members. Thus, each linkage unit 3 0 allows rotational movement about one axis with one body member 4, 6, 8, 10, and rotational movement about an orthogonal axis with its other conjoined body member 4, 6, 8, 10. In this way, the linkage unit 30 allows the body members 4, 6, 8, 10 relative movement about two axes (based along the axes of the pins 34) . The relative movements between the linkage units 30 and body members 4, 6, 8 and 10 are resisted and extracted by power extraction means which extract power from this relative motion. The power extraction means may be any suitable means adapted to be activated by this relative motion. One such means is a damping element in the form of a hydraulic ram and piston assembly. In the present embodiment of the invention shown, two hydraulic ram assemblies 40 are provided at each end of the linkage unit 30, and on each side of the linkage unit-body member linkage means. The parts of the assemblies 4 0 between the unit 3 0 and end caps 38 will generally be enclosed by flexible seals 41 to accommodate axial motion of the ram assemblies 40 extending and retracting, as known in the art. Figures 9 and 10 show internal details of the linkage unit 30. One set of bearings 32 are shown, set at a substantially orthogonal angle to two hydraulic ram assemblies for connecting the shown face of the linkage unit 30 to a body member 4, 6, 8, 10. Ram assemblies 42A, 42B are substantially sway rams, as shown in Figure 10. However they are not solely sway rams as the rams 42A, 4 2B can be used to induce a cross-coupled response which may be tuned to be resonant in small waves to increase power capture and which may be set in large waves to limit power absorption and maximise survivablity. One'end of these rams 42A, 42B are rotatably attached to a pin 45 within a cavity 35 located in the cap-end 3 8 of an adjacent body member 4, 6, 8, 10. Figure 10 shows orthogonally located hydraulic ram assemblies 44A, 44B which are substantially, but not solely, heave rams which can also be used to induce a cross-coupled response as described in the above paragraph. These heave rams 44A, 44B are attached to a pin 4 5 within a cavity 35 located in the cap end 38 of an opposing adjacent body member 4, 6, 8, 10. Heave ram 44A and sway ram 42A are connected to a first main manifold 46 which can feed towards a Figure 11a shows schematically a first useable split hydraulic circuit system inside the linkage unit 30. The first circuit system is effectively split by axis of rotation, such that sway rams 42A and 42B serve a first circuit by feeding into one high pressure accumulator 84, and heave rams 44A and 44B serve a second circuit feeding into a second high pressure accumulator 86, all through the outlet valves 70. The pressured oil operates respective hydraulic motors 52, 54, which can operate respective electrical generators 60, excess pressure going through respective heat exchanges 62 to low pressure reservoirs 88 and 90, before returning to the rams 42, 44 through inlet valves 72. The two circuits meet at the common central manifold 48, such that for normal operation, the two circuits can run linked, thereby increasing efficiency, especially in small seas. Each half of the hydraulic circuit can feed the separate hydraulic motors 52, 54, set to allow generation when the system is to be linked or to be separated. With the circuits linked in small seas (when the system is below 50% power), this allows a single generator to be fed by both hydraulic circuits. This minimises the working hours of each generator, and allows the single generator to run at a nearer full load, dramatically increasing efficiency. In the event of a fault or leak with one half of the system, the circuits can be separated to allow the other half to function independently, maintaining failure, this also provides the necessary thermal load. The hydraulic oil used by the apparatus is preferably specified to be biodegradable, and nontoxic to water organisms. The linkage unit 3 0 includes one or more access portals such as hatches. In the embodiment shown in the accompanying drawings, the linkage unit 30 has a first man-assessable hatchway 64 and a larger main-assessable hatchway 66. The linkage unit 30 may also include a separate or equipment loading hatchway. Figure 12 shows a further schematic part cross-sectional perspective of the linkage unit 30 attached to a buoyant body member 6. Parts of the linkage unit 3 0 have not been shown in order to better illustrate the position of parts of the power conversion units already installed 92, and a further part 94 being installed through the main-access hatchway 6 6 . By housing all the significant components and parts for the power extracting in one linkage unit, this allows the unit to share components such as manifolds, pipework, fittings, mountings, power supply and batteries, etc. within a single unit, compared with previous known wave energy converters, including that shown in WO 00/17519. The unit 30 is therefore adapted fox* maintenance or repair within A further advantage concerns the avoidance of the use of a joint spider 14 as shown in Figures 2-4. In this arrangement, the rams form the main load path through the whole apparatus. This is because the loads pass from one body member, through the main bearing into the rear of the hydraulic ram, and then pass straight through the module into the rod end mount in the end of the next body member. In the present invention, loads through the linkage unit 3 0 are reduced to shear loads, other environmental loads, and any small imbalance loads due to the differential areas of the rams. This means that the configuration can be more structurally efficient. Moreover, as loads on the linkage unit structure are small, access portal size can be significantly larger making installation of . the components much easier. Lower structural loads around access portals also allows simpler sealing systems to be used. The apparatus 2 is referenced predominantly against itself rather than against the shore or the seabed. This self referencing is achieved by the apparatus 2 being of length comparable to the incident wavelength, and the apparatus 2 being orientated relative to incident waves in a direction such that the apparatus 2 spans at least two crests of the incident waves. The configuration and orientation of individual joints, and the type and rating of individual power extraction means which comprise a particular The mooring system may also provide significant physical restraint or excitation to the apparatus so as to modify the overall response. In calm weather, where wavelengths are relatively short, and wave amplitudes are small, there is a requirement to maximise power absorption by the apparatus. In extreme weather, where wavelengths are longer and wave amplitudes are larger, survival of the apparatus is of greater importance than power absorption efficiency. The total length of the assembled apparatus is therefore selected to be sufficiently long to provide adequate self referencing of itself in short wavelengths where not much power is available and there is a requirement to maximise power absorption, and sufficiently short to 'hide1 in long wavelengths associated with storm waves in order to survive. If the wavelength is much greater than the length of the apparatus 2, then it cannot extend from peak to peak, and the maximum movement of any part of the apparatus 2 relative to any other part is less than the amplitude of the wave, so that it 'hides' in the long wavelength. In other words, the apparatus 2 loses the ability to reference itself against the wavelength. This effect is further discussed in WO 00/17519. The present inventicn provides a single, compact, self-contained and manufacturable unit. This lends itself to efficient, centralised manufacture and testing., for shipment to a final assembly site. Thus, the main body members could be manufactured near the deployment site, and would require minimal fit-out before final assembly with the linkage unit. Further, the linkage units can be fully tested prior to transportation and installation on-site. Moreover, all the high technology, high valve and data components are within a single unit. Claims 1. Wave power apparatus comprising: a plurality of buoyant elongate body members, at least one adjacent pair of body members being interconnected by a linkage unit to form an articulated chain, each body member of said pair being connected to the respective linkage unit by linkage means permitting relative rotation of the body members; power extraction means adapted to resist and extract power from the relative rotation, the power extraction means being located substantially within each linkage unit; and wherein each linkage unit is arranged to permit relative rotation between the linkage unit and a first body member about a first axis of rotation at a first end of the linkage unit, and to permit relative rotation between the linkage unit and a second body member about a second axis of rotation at a second end of the linkage unit. 2. Apparatus as claimed in claim 1, wherein the body members are arranged consecutively in an articulated apparatus, each adjacent pair of body members being interconnected by a linkage unit to form an articulated chain. 3. Apparatus as claimed in claim 1 or 2, wherein the or each linkage unit has a longitudinal length substantially shorter than the body members. 4. Apparatus as claimed in any preceding claim, in which the body members substantially comprise hollow members devoid of active components. 5. Apparatus as claimed in any preceding claim, wherein each body member has one or more end caps with corresponding linkage means to marry with the linkage means of the linkage unit. 6. Apparatus as claimed in any preceding claim, wherein the power extraction means includes a hydraulic ram assembly. 7. Apparatus as claimed in claim 6, wherein the hydraulic ram assembly comprises a plurality of rams. 8. Apparatus as claimed in claim 6 or 7, wherein the power extraction means includes a hydraulic ram assembly for each axis of rotation. 9. Apparatus as claimed in claim 8, wherein the power extraction means includes two hydraulic ram assemblies acting about each axis of rotation. 10. Apparatus as claimed in claim 5, wherein the end caps have a number of cavities to receive respective ends of the power extraction means. 11. Apparatus as claimed in any preceding claim, wherein the power extraction means has at least one seal to prevent ingress of water into the linkage unit and/or body members. 12. Apparatus as claimed in any preceding claim, wherein the linkage unit includes one or more power generation or storage means connected to one or more of the power extraction means. 13. Apparatus as claimed in claim 12, wherein the linkage unit includes a first power generation means connected to one or more power extraction means at one axis of rotation, and a second power generation means connected to one or more power extraction means at the other axis of rotation. 14. Apparatus as claimed in claim 13, wherein the first or second power generation means is connectable to at least one power extraction means from each axis of rotation, such that the restraint of the linkage unit is maintained in the event of failure of one of the power extraction or generation means. 15. Apparatus as claimed in claim 13, wherein the first and second power generation means is connectable to one or more of the power extraction means from one or both axes of rotation, such that when the apparatus is operating at partial capacity, the one or more power extraction means is connected solely to the first or second power generation means. 16. Apparatus as claimed in any preceding claim, wherein constraint is applied to each power extraction means of the linkage unit in order to induce a cross-coupled response which may be tuned to be resonant in small waves to increase power capture and which may be set in large waves to limit power absorption and maximise survivability. 17. Apparatus as claimed in any preceding claim, wherein the apparatus includes one or more of a ballasting system, mooring system, and means to apply a roll bias angle to the axes of rotation. 18. Apparatus as claimed in any preceding claim, wherein the linkage unit includes access means, such as one or more hatches, to allow inspection, repair . and maintenance on or off site. 19. A linkage unit for use in the apparatus of claim 1, comprising: linkage means for interconnection between the body members permitting relative rotation at either end of the unit; power extraction means adapted to resist and extract power from the relative rotation of the body members; the power extraction means being located substantially within the linkage unit; and wherein the linkage unit is arranged to permit relative rotation between the linkage unit and a first body member about a first axis of rotation at a first end of the linkage unit, and to permit relative rotation between the linkage unit and a second body member about a second axis of rotation at a second end of the linkage unit. 20. A linkage unit as claimed in claim 19, wherein the power extraction means includes a hydraulic ram assembly. 21. Apparatus as claimed in claim 20, wherein the hydraulic ram assembly comprises a plurality of rams. 22. A linkage unit as claimed in claim 21, wherein the power extraction means includes a hydraulic ram assembly for each axis of rotation. 23. A linkage unit as claimed in claim 22, wherein the power extraction means includes two hydraulic ram assemblies acting about each axis of rotation. 24. A linkage unit as claimed in any of claims 19 to 23, wherein the power extraction means has at least one seal to prevent ingress of water into the linkage unit and/or body members. 25. A linkage unit as claimed in any of claims 19 to 24, wherein the linkage unit includes one or more power generation or storage means connected to one or more of the power extraction means. 26. A linkage unit as claimed in claim 25, wherein the linkage unit includes a first power generation means connected to one or more power extraction means at one axis of rotation, and a second power generation means connected to one or more power extraction means at the other axis of rotation. 27. A linkage unit as claimed in claim 26, wherein the first or second power generation means is connectable to at least one power extraction means from each axis of rotation, such that the restraint of the linkage unit is maintained in the event of failure of one of the power extraction or generation means. 28. A linkage unit as claimed in claim 27, wherein the first and second power generation means is connectable to one or more of the power extraction means from one or both axes of rotation, such that when the apparatus is operating at partial capacity, the one or more power extraction means is connected solely to the first or second power generation means. 29. A linkage unit as claimed in any of claims 19 to 28, wherein constraint is applied to each power extraction means of the linkage unit in order to induce a cross-coupled response which may be tuned to be resonant in small waves to increase power capture and which may be set in large waves to limit power absorption and maximise survivability. 30. A linkage unit as claimed in any of claims 19 to 29, including access means, such as one or more hatches, to allow inspection, repair and maintenance on site. 31. A method of extracting power from waves comprising the steps of: deploying an apparatus as claimed in any of claims 1 to 18; orientating the structure such that a front end of the structure faces into the oncoming waves; and extracting the power absorbed in the or each linkage unit. 32. A method of manufacture of apparatus according to claims 1 to 18, comprising the step of: interconnecting each pair of adjacent body members of the apparatus with a linkage unit according to claims 19 to 30. 33. The method of claim 32, wherein the body members and linkage unit(s) are connected together close to or on site. 34. The method of claim 32, wherein the linkage unit(s) are fully assembled and tested before being transported to site.

Documents:

2888-chenp-2005 abstract-duplicate.pdf

2888-chenp-2005 claims-duplicate.pdf

2888-CHENP-2005 CORRESPONDENCE OTHERS.pdf

2888-CHENP-2005 CORRESPONDENCE PO.pdf

2888-chenp-2005 description (complete)-duplicate.pdf

2888-chenp-2005 drawings-duplicate.pdf

2888-CHENP-2005 FORM 1.pdf

2888-CHENP-2005 PETITIONS.pdf

2888-CHENP-2005 POWER OF ATTORNEY.pdf

2888-chenp-2005-abstract.pdf

2888-chenp-2005-claims.pdf

2888-chenp-2005-correspondnece-others.pdf

2888-chenp-2005-correspondnece-po.pdf

2888-chenp-2005-description(complete).pdf

2888-chenp-2005-drawings.pdf

2888-chenp-2005-form 1.pdf

2888-chenp-2005-form 3.pdf

2888-chenp-2005-form 5.pdf

2888-chenp-2005-others.pdf

2888-chenp-2005-pct.pdf