WO2020257909A1

WO2020257909A1 - Interconnected self-orienting wave energy collectors

Info

Publication number: WO2020257909A1
Application number: PCT/CA2020/000072
Authority: WO
Inventors: Rajesh Gaonjur
Original assignee: Rajesh Gaonjur
Priority date: 2019-06-25
Filing date: 2020-06-15
Publication date: 2020-12-30
Also published as: CN115023546A; CA3047760A1; EP3983666A1; EP3983666A4

Abstract

A wave energy harnessing system comprising of a plurality of wave energy devices coupled together, to form high capacity installation. The wave energy device includes a buoyant body which maintains a permanent orientation relative to the surface of the ocean, while the power take-off (PTO) would self-align in the direction of the incoming waves. The power take-off is completely enclosed, above the waterline and easily accessible. The buoyant body is coupled to the buoyant bodies of other similar wave energy devices by flexible or articulating coupling means. The wave energy devices are arranged in arrays or any other suitable layouts, to form large connected floating structures of desired sizes, and power systems of various capacities. Interconnection cables linking the PTOs are secured on cable supports provided between the wave energy devices. Few underwater infrastructures are required. The moorings and the underwater transmission cable are shared by the whole installation.

Description

INTERCONNECTED

SELF-ORIENTING WAVE ENERGY COLLECTORS

FIELD OF THE INVENTION

The present invention generally relates to devices and methods for harnessing energy from ocean waves, particularly suitable for large scale energy production.

BACKGROUND OF THE INVENTION

Waves from oceans have the potential to become a major source of sustainable and renewable energy. Wave energy is far more concentrated and reliable, when compared to solar or wind energy. Oceans cover about two-third of the planet, and wave energy can be harnessed practically anywhere on the ocean surface. It is estimated that the total wave energy resources available can exceed the entire global energy need. Large scale energy production from waves, together with other renewable energy sources could almost eliminate the need of fossil energy, and save our planet from pollution and global warming. Global warming is a very serious issue which need to be addressed urgently.

Wave energy has proven quite difficult to harness, even after decades of research and genuine interest. A reliable and cost effective method of harnessing wave energy remains to be found. To this day, while an impressive number of concepts have been proposed, there is still no commercial scale energy production from waves, except some few ongoing experiments. The constantly changing energy flux carried in the waves leads to a great diversity of devices, as designers continuously explore best possible methods to harness wave energy. The different environmental conditions offshore and near the shore, largely influence the designs of these wave devices, and how they operate. There are wave devices that float, those that sit on the ocean floor, and those installed on the shore. The large diversity of concepts may have actually slowed down the commercial development of wave energy, as winning concepts find it more difficult to immerge from the lots, and go through further refinements.

The harsh environment of the ocean greatly affects survivability and reliability of equipments. Violent storms are frequent, and the sea water is corrosive. Cost of installation in the open sea and construction of underwater infrastructure, are much higher compared to land based infrastructures. The ocean environment also makes access to installations particularly difficult for routine maintenance and repairs. Another difficulty lies in the fact that wave energy devices are mostly not scalable to be economically viable. The optimum size of a wave device depends on the size and frequency of the waves, and is usually much less than one megawatt. A wave energy installation of reasonable power capacity would generally comprise of a large number of wave devices, spread over a wide area of the ocean. This significantly add to installation cost, as more underwater cables are required to interconnect these dispersed wave devices, and the need of as many mooring systems to secure these devices. The cost of construction, installation, and exploitation of such wave energy installations is the main reason which has prevented the development of wave energy.

A basic approach to reduction of cost is the sharing of basic installations among as many wave energy devices, or power take-offs within an installation. Several power take-offs may be mounted on a single wave device, or several devices may be installed very close to each other. This allows sharing of infrastructures and equipments more effectively. Close proximity of wave energy devices allow significant reduction in the amount of interconnecting cables and various monitoring equipments. Group of connected wave devices have a higher capacity factor, as the combined power is smoother, which allow reduction in the installed capacity of power equipments being shared. Significant economy is also achieved during installation, commissioning and maintenance. In several prior arts, power take-offs are often mounted close together, in order to improve cost effectiveness.

The patent WO 00/17519 known as the Pelamis and the patent US 8,806,865, are examples of wave energy concepts where several power take-offs are mounted on single floating wave devices. However the modules comprising these wave devices are connectable only in single rows, and in limited in numbers. These wave devices are generally constructed as long as it is technically possible to operate. They are usually oriented in the direction of the waves, and they take up large amount of marine space to account for changes in wave direction. Some patents such as, US 2011/0057448 A1 and WO 2010/082033 A3 overcome this shortcoming by disclosing concept of devices where larger numbers of modules are connected in several arrays, and which does not need to be oriented in the direction of the waves. However, all these wave devices remain extremely vulnerable to the condition in the ocean. While the power take-off of these devices may be disconnected for self- preservation, the external articulating members and joints comprising these wave devices remain exposed to extreme mechanical forces resulting from the waves. The risk of water infiltration through defective seals at these articulating members is also a permanent concern. Patent WO 2014/026219 A1 is also another wave device comprising of several connected modules, but is most suitable for shallow water.

Wave energy devices with completely enclosed hulls, are the most suitable in order to harness the most intense offshore waves, and harmlessly endure the worst condition that prevail. The enclosed articulating or reciprocating elements of the power take-offs are less exposed to the direct force of the waves, and the risk of water infiltration is also greatly reduced. However, these wave devices can be operated as standalone units within energy farms at some distance from adjacent devices, making it difficult to share most infrastructures. While heaving type devices would operate in all direction of waves, they are subjected to interference by similar devices in the proximity. Pitching type wave devices, as in patent US 2011/0089690 A1 also need some operating distances, as they need to be oriented in the direction of the waves. In order to operate in waves from all direction, pitching-type wave devices, as in patent US 8,129,854 B2 have to rely on a plurality of power take-offs, aligned in several directions. The design is rendered complex, and the power takeoffs are not fully utilised.

If wave energy is to become a reliable and popular energy source of the planet, it is most desirable that wave energy devices should be able to harness the higher concentration of energy contained in the offshore waves, and most cost effectively. Another desirable feature is that these wave devices may also be used in most diverse ocean environments. Hopefully, the abundant numbers of wave energy devices concepts may be narrowed down to a fewer most suitable concepts, which when mass produced on a larger scale would further lead to reduction in cost.

OBJECTS OF THE INVENTION

The main object of the invention is to provide a method and system of harnessing energy from ocean waves, while reducing cost of construction, installation and maintenance.

Another object of the invention is to provide for wave energy harnessing devices which can operate in diverse marine environments, with all critical components sheltered within waterproof enclosures, well above the waterline for easy access.

It is also another object of the invention to provide for wave harnessing devices which are particularly suitable for the use of conventional rotary electrical machines and electronic equipment similar to those used in wind energy conversion, which are largely available and with proven track record.

A further object of the invention is to provide for wave energy harnessing devices which can operate without causing harm to marine life, and is not disrupted by debris in the oceans.

Yet another object of the invention is to provide for versatile wave energy harnessing devices which can be operated offshore in the deep seas, in shallow lagoons, or even nearer to the shoreline.

SUMMARY OF THE INVENTION

In this present invention, several embodiments of wave energy systems and related components are disclosed. Herein, wave energy harnessing devices are generally referred as wave energy collectors. The most prominent features will be discussed briefly in this summary, without limiting the scope of the invention as expressed by the detail description, drawings and claims that follows. In accordance with embodiments of the invention, a system of interconnected devices for harnessing energy from waves is disclosed, comprising of a plurality of wave energy devices which are electrically and mechanically coupled together, forming a single large floating structure with a high combined power capacity. The use of underwater cables to interconnect the multitude of devices is eliminated, while underwater infrastructures and moorings are considerably reduced. The modular concept of the invention makes possible the construction of wave devices and installation of diverse power capacity, with relative ease. A large numbers of these wave devices may be assembled in a port facility and then tug to installation site ready for use. The power capacity of these installations may even be significantly upgraded if required at a later stage, as more wave devices may be coupled to the existing installations without the need of additional underwater infrastructures. All these features contribute to the reduction of cost during construction, installation, and maintenance. In comparison, current method to harnesses large amount of power from a given installation is by the use of a plurality of interconnected wave devices within energy farms. Each device within such energy farm has to be maintained at a safe reasonable distance from each other by independent moorings, and then interconnected by underwater power cables. High numbers of wave devices are required. The power capacity of each wave device is usually limited by the characteristics of the waves, and scaling up of these devices is usually not possible.

In accordance with other embodiments of the invention, a wave energy device is disclosed, comprising preferably of a single power take-off which would rotate and self-align instantly in the direction of the incoming waves, while the external buoyant body of the device would maintain a permanent orientation. Energy from the waves is extracted as the buoyant body of the device would pitch and roll from side to side in any direction. The buoyant body of the wave device may be mechanically couple by some suitable means to a multitude of other similar wave devices in any numbers of rows and columns, forming a system of interconnected devices as referred earlier. As a matter of fact, it is of highest importance that these devices harness energy efficiently from any direction of waves, as it is technically not always practical to constantly having to orient a high numbers of interconnected devices with the changing direction of the waves. Existing pitching-type wave devices are mostly designed to operate only in a given direction of waves, and hence cannot be coupled together. A pitching-type wave energy device designed to harness incoming wave from all direction would generally, according to prior art, comprise of a plurality of power take-offs within the device, each aligned to handle waves in a particular direction most efficiently. The need of higher numbers of power take-offs only add to the complexity and cost of the installation. The use of less efficient and less reliable hydraulic systems is then mostly preferred due to cost consideration.

In accordance with yet another embodiment of the present invention, a large standalone wave energy device is disclosed, comprising of a plurality of self orienting power take-offs mounted on a single floating structure. While comparable in several aspects with the system of interconnected wave devices introduce earlier, such a single device of high capacity allow for further economy of scale.

The features, functions, and advantages in various embodiments of the present invention, can be achieved independently or may be combined in yet other embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the following drawings: FIG. 1 is an isometric view of a group of wave energy collectors interconnected in an array configuration, floating in the ocean.

FIG. 2 is a top view of a group of wave energy collectors interconnected in a different configuration, floating in the ocean.

FIG. 3 is a side view of a coupling means used to couple two adjacent the wave energy collectors, as shown in FIG. 1 and FIG. 2.

FIG. 4 is a side view of a group of interconnected wave energy collectors, pitching in the waves. FIG. 5 is a side sectional view of a completely enclosed nacelle, showing the main components of the Power Take-off.

FIG. 6 is a top sectional view of the nacelle shown in FIG. 5.

FIG. 7 is a side view of the nacelle in FIG. 5 in a pitched position during operation, shown with some internal details.

FIG. 8 is a side sectional view of another embodiment of a nacelle with some externally mounted components.

FIG. 9 is the top view of another embodiment of a wave energy collector, comprising of a nacelle shown in FIG. 8. FIG. 10 is a side view of the wave energy collector shown in FIG. 9.

FIG. 11 is a top view of several wave energy collectors shown in FIG. 9 coupled together, comprising of completely enclosed nacelles.

FIG. 12 is a side view of interconnected wave energy collectors shown in FIG. 9, pitching in the waves. FIG. 13 is a top view of another embodiment of a wave energy collector, comprising of a plurality of enclosed nacelles as shown in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention are set forth in the detailed description that follows herein and the accompanying drawings. The drawings are not to scale and are for illustration only. The detailed description is subdivided into several sub-sections for clarity, discussing different aspects of the invention. Corresponding components and components having similar functions in the drawings are designated by the same numerals, except in cases where specific parts are referred. Embodiments of the invention may have different structures and shapes, without departing from the scope of the invention. Some used terms are also defined for the purpose of clarity. The term “wave energy collector”, herein refers to wave energy harnessing devices.“WEC” or“WECs”, is used as an abbreviation of the word“wave energy collector”. The terms“wave energy device” or“wave device” also generally refer to embodiments of the wave energy harnessing devices. Wave energy harnessing devices are known by several other names in different literatures.

“Pontoon” herein refers to a floating body which may be completely closed or open at the top similar to the hull of a floating vessel, purposely designed to have pronounced pitching and rolling movements when interacting with the waves. The “pontoon” would be constructed in relation to the dimension of the wave, in order to pitch most efficiently.

“Buoy” refers to a floating body of smaller dimension relative to the ocean waves, which enable them to heave most efficiently in the waves. The“buoys” may be of any shape, generally completely enclosed to prevent ingress of water.

“Power Take-Off’ abbreviated as “PTO”, refers to a power extraction means installed within a WEC for transforming the energy from waves into a useful form of energy. The“PTO” is operated by movement of the WEC relative to a fix reference, or by the relative movement of articulating members connected to the“WEC”. The wave energy is transformed into useful energy, in the form of hydraulic, pneumatic, or electrical energy.

“Flexible coupling device” or“coupling device” in this detail description refers to a wide range of devices for the purpose of securing two separate bodies, while allowing the connected bodies a certain amount of movements relative to each other, with none or little mechanical resistance. This includes any mechanical coupling devices which can perform this function, such as universal joints, but also chains, ropes, or connecting members having elastomeric properties. “Flexible coupling devices" may comprise of a single or several devices assembled together.

“Power conduit” herein refers to connecting elements used for the transmission of energy in the formed of fluid or electricity.“Power conduits” would comprise of hollow pipes when energy is carried in fluids, such as air, water, or oil. The term“cable bus” is also a type of“power conduits” comprising of electrical cables for transmission of electrical energy. “Cable support” refers to various devices and structures which may provide support for“cable bus” or“power conduit" laid across two adjacent WECs which are coupled together by “coupling device”. This include support structures, cable channel, cable trays, cable ladders, articulating cable carriers, conduits, including aerial cable supports.

General concept

Embodiments of the invention generally comprise of a plurality of independent wave energy collectors (WECs) which are coupled together mechanically and electrically, so as to form large connected floating structures. In FIG. 1 , a group of WECs 20 is shown coupled together in an array configuration within an installation. In FIG. 2, another group of WECs 20 is shown coupled together in a different configuration. The WECs 20 are usually of similar size and power capacity to facilitate interconnection. The WECs 20 may be coupled together forming installations of various shapes, to maximise the absorption of wave energy, better resist rough weather, or to fit certain installation site. For example, rows of interconnected WECs 20 may stretch along the shoreline over long distances, facing the incoming waves. By absorbing as much energy from the waves, the arrays of WECs 20 may also act as a wave breakers preventing coastal erosion. In offshore installation, the WECs 20 may be bundled in some tight configurations to better resist rough weather.

The WECs 20 may be designed to various scales, in order to operate either in large offshore waves or in relatively smaller waves near the shore. Embodiments of WECs 20 would generate between a few kilowatts to several hundreds of kilowatts (KW) of energy, depending on the dimension of the WECs 20 and the wave characteristics, such as intensity and wavelength. A WEC 20 may be operated as a single standalone unit, but in general a single installation would comprise of several numbers of interconnected WECs 20, ranging from a few to several thousands in numbers, with the aim to produce several megawatt or even gigawatt of electrical energy. Installation of such high capacity can be easily deployed as no extensive underwater infrastructures is required, except the laying of underwater power transmission cable to the shore, and moorings to secure the installation in the ocean. Large numbers of WECs 20 may be coupled together in port facilities, and then tugged in the open sea to the installation site ready for operation. Power capacity of a given installation may even be substantially increased by coupling additional WECs 20, without the need of additional moorings or power transmission cable. Embodiments of the invention, because of the ease of deployment and installation, can be use as temporary power installations in coastal areas following disasters and major power network failures.

As shown in FIG.1 and FIG. 2, each of the WECs 20 includes a pontoon 21 and a nacelle 22 firmly secured at the center. The nacelle 22 is a waterproof enclosure which houses the Power Take-Off (PTO). In preferred embodiments of the invention, the PTOs generate electrical energy as the nacelles 22 pitch and roll about the horizontal plane together with the pontoons 21. The pontoon 21 of a given WEC 20 is coupled to the pontoons 21 of adjacent WECs 20 within an installation by flexible coupling devices 23. This allows each of the WECs 20 to move freely about the joints of the coupling devices 23. A cable bus 24 of appropriate power capacity connects and combines all the power generated in the PTOs. Waterproof cable entries are provided in the nacelles 22 for interconnection of the PTOs. The cable bus 24 is properly secured to the side of the pontoons 21, and to the cable supports 25 where the cable bus 24 is laid across the coupling devices 23. The cable supports 25 allow free movements of the interconnected WECs 20, while preventing the cable bus 24 from potential damages.

The combined power of the interconnected PTOs is usually transmitted by a single underwater transmission cable 26 to the power grid on shore. But certain large embodiments of the invention may comprise of several underwater transmission cables 26 for increased reliability. The underwater transmission cable 26 may also connect the installation to other groups of wave energy devices, located at some distance within an energy farm. In other use of the invention, the power may be consumed by manufacturing and processing plants installed within the WECs 20, or on separate floating platforms. The energy harnessed may be used for undersea mining in the proximity of the installation, or the production of fresh water. A very practical use of wave energy is the production of hydrogen from the seawater, which can then be transported by ships or pipelines. Embodiments of the invention may also be mounted on watercrafts of appropriate designs, and the energy from the waves used for propulsion of the watercrafts.

Main structures

The WEC 20 is designed in shape and size so as to interact with the waves, and harnessed wave energy most effectively. The pontoon 21 may be constructed in the shape of a buoyant ring, as shown in FIG. 1 and FIG. 2. The buoyant edge of the pontoon 21 further from the center of the nacelle 22 provides better leverage and torque required to operate the PTO. The nacelle 22 is secured at the center of the pontoon 21 by a number of spars 27, or any alternative structural framework, or platform to ensure integrity of the construction. The spars 27 may be made steel frames members, such as hollow pipes or steel sections. Steel must be galvanised, painted, or coated by some other protective materiel to better resist corrosion. Other construction material, such as wood, fibreglass, or similar synthetic materials may be used for construction of the spar 27, provided they are of adequate size to endure the work load. A number of spars 27 are used distributed evenly about the perimeter of the pontoons 21 to ensure integrity of the construction. In FIG. 1, the nacelle 22 is shown secured to the pontoon 21 by four set of spars 27. In FIG. 2, the nacelle 22 is shown secured by eight set of spars 27. As an alternative to pontoon 21 , a plurality of independents floating bodies may be disposed around the nacelle 22, each secured directly to the nacelle 22, or by the use of a plurality of spars 27. In other embodiments of the invention, the nacelle 22 may be secure at the center of the ring- shaped pontoon 21 by a plurality of support cables or ropes under tension. The cables are used as an alternative to rigid spar 27 in a construction similar to wire wheel, where the central hub is secured to the rim by cables under tension. In some other embodiments of the invention, the pontoon 21 may be constructed as a circular hull like platform. The nacelle 22 may then be mounted above at the center, or inside the hollow body of the hull.

The circular shape of the pontoon 21 allows efficient spatial distribution of the WECs 20 when they are coupled together. The interconnected pontoons 21 can then move about the coupling devices 23 with minimum interaction with each other. The symmetrical circular shape of the pontoon 21 also allows energy to be harnessed from waves in all direction with same uniformity. The WEC 20 would generally have the center of gravity and the center of buoyancy vertically aligned, in order to ensure flotation stability and correct operation of the PTO. The WECs 20 which are used as standalone units may be designed with a lower center of gravity to enhance flotation stability in rough weather condition. Embodiments of the invention comprising of large numbers of interconnected WECs 20 are naturally stable in rough weather.

The pontoons 21 are robust construction so as to withstand extreme weather condition. The design of the pontoons 21 may vary widely in different embodiment of the invention The pontoons 21 may be made of metal or other synthetic material such as fibreglass, and air-filled to ensure flotation. The pontoon 21 is built to required dimension, so as to enable the WEC 20 to float and also provide the forces required to operate the PTO in the nacelle 22. The pontoon 21 may be entirely constructed of some solid lightweight material of density lower than water. Pontoons 21 with air filled cavities would generally comprise of several separate airtight compartments to ensure integrity in case of damage. The pontoons 21 may also be made of soft inflatable material, such as rubber or equivalent synthetic material, as a cost effective alternative. Pontoons 21 made of soft material also effectively cushion the contacts between each other during operation. Additional internal or external reinforcement structures may be required to ensure stiffness and strength of the pontoons 21. Pontoons 21 may be constructed in other cost effective shapes, depending on the manufacturing means and material of construction. As such, the pontoons 21 may be constructed as regular polygons with a number of sides, instead of being circular. The pontoon 21 may also comprise of a plurality of independent modular segments assembled and secured together in required numbers, in order to accommodate WECs of different dimension. As the pontoons 21 within an installation of interconnected WECs 20 would be constantly rubbing and bumping with each other, the sides of the pontoons 21 may need to be protected from premature wear and damages. Marine fenders, bumpers, old tires, or pads may be mounted around the perimeter of the pontoons 21 for additional protection where required. The parts of the WEC 20 exposed to seawater may need some antifouling treatment, but in general fouling do not seriously affect performance of the WECs 20, because of the absence of any external articulating members or joints. Furthermore, it should be noted that the proliferation of marine life in the underside of the WECs 20 may be rather beneficial to the marine ecosystem.

The coupling devices 23 are used only as a means to secure the pontoons 21 together, and take no part in the operation of the PTOs. The coupling devices 23 also allow each of the pontoons 21 to move freely with the waves, so that the PTOs mounted on each pontoon 21 can harness energy from the waves. So, the coupling devices 23 are designed to provide as little mechanical resistance as possible, to the movement of the pontoons 21. The coupling devices 23 are also designed to resist extreme mechanical forces in all weather conditions. The sides of the pontoons 21 where the coupling devices 23 can be reliably mounted, are reinforced in order to endure the forces involve. The coupling devices 23 are positioned where required on the side of the pontoons 21 , according to the layout of the interconnected WECs 20 in a given installation. The coupling devices 23 can be constructed in a variety of ways. Coupling devices 23 may comprise of one, or a combination of several standard off-the-shelves mechanical devices, such as universal coupling, spring coupling, elastomeric coupling, bellow coupling, knuckle coupling and others. Coupling devices 23 may be custom-made. Coupling devices 23 may also comprise of other components such as spring, ropes, chains, fabrics, used tires, and any flexible material. When large numbers of WECs 20 are coupled together, their movement may become significantly damped as the pontoons 21 would pull and push mutually on each other, hence reducing the overall energy extraction efficiency. This problem is attenuated by the use of coupling devices 23 which are able to extent and contract in length substantially. These embodiments of coupling device 23 may then also comprise of telescopic joints, springs, material of elastomeric properties, or made of articulating members, so as to allow the coupling device 23 to stretch and contract by the amount required. Each of the WECs 20 within such large installation, is then able to surge and sway sideways more freely within the extra space provided, hence reducing the mechanical forces the WECs 20 may exert mutually on each other.

An example of a coupling device 23 is shown in FIG. 3, comprising of standard marine equipment commonly use to secure floating structures and boats. The same type of coupling means is used in embodiment of the invention shown in FIG. 1 and FIG. 2, but any other alternative coupling means which meet the operation requirements could have been used. As shown in FIG. 3, a marine fender 31 of cylindrical shape is secured between the pontoons 21 of two adjacent WECs 20 by mooring pendants 32. The mooring pendants 32 are maintained slack, which allow the pontoons 21 to move relative to each other with negligible mechanical resistance. The mooring pendants 32 may comprise of chains, or synthetic ropes. The mooring pendants 32 may also have some elastic properties to better endure and absorb shocks. Mooring rings 33 are provided on the side of the pontoons 21 and the marine fender 31. The mooring springs 34 of appropriate load capacity provide a graded restraining force, and manage the excess slack in the mooring pendants 32. The mooring springs 34 are mounted on the sides of respective pontoons 21 and the marine fender 31. Marine fenders 31 of suitable size and diameter are selected according to the size of the pontoons 21, in a given installation. The marine fenders 31 may float between the sides of the pontoons 21 , or secured above the ocean surface or waterline 35 as shown in FIG. 3. Marine fenders 31 are usually made of synthetic material, such as rubber which is adequately deformable, pliable, and with good cushioning properties. The marine fenders 31 may be filled with air or foam. Marine fenders 31 of other shape and design may be used to improvise other form of coupling device 23. Alternative mounting arrangements may be used to secure the marine fender 31 to the pontoons 21.

FIG. 3 also shows an example of a cable support 25 which carry the cable bus 24 between two adjacent pontoons 21 , in order to connect the PTOs in the respective nacelles 22. Cable supports 25 are placed along the path of the cable bus 24 where require, and are firmly secured to the side of the pontoons 21. The cable support 25 may comprise as shown, of an articulated cable carrier or tray. The members comprising the cable support 25 articulate about a plurality of hinges 36, hence the cable support 25 opposes no resistance to the free movements of the pontoons 21. The cable bus 24 is secured on the cable support 25 and the side of the pontoons 21 by cable clamps 28 or any other appropriate means. The cable bus 24 would have a reasonable amount of excess length in order to allow bending around the articulations of the cable support 25. The articulations of the cable support 25 must accommodate the most extreme movements between the pontoons 21 and the marine fender 31 , without causing damage to the cable bus 24.

The cable supports 25 may be constructed in a number of various other ways. The cable supports 25 may comprise of flexible synthetic material which can easily twist, stretch and bend. The segment of the cable bus 24 across the flexible coupling device 23 may comprise of spiral power cable, so as to easily stretch and contract. The cable bus 24 may be secured by some aerial means across the pontoons 21. In some other embodiments of the installation, cable supports 25 may not be used. The cable bus 24 may be secured directly to coupling device 23 of appropriate designs. In other embodiments of the invention, the cable bus 24 may be allowed to hang loose and free between the connected pontoons 21 , or even trail in the sea water. In these cases, the cable bus 24 may be provided with additional protective sheath for protection against mechanical damage due to possible interaction with the WECs 20, and protection against the seawater. In other embodiment of the invention, the coupling devices 23 may include internal cableways for the cable bus 24. Internal cableways may be also provided within the pontoons 21, so that the cable bus 24 between the interconnected WECs 20 is completely internal and not visible from the outside. It is understood that power conduits other than electrical cables may be used to carry the harnessed energy from the interconnected WECs 20, in other embodiments of the invention. Such power conduits may comprise of network of pipes or hoses which carry fluids from the PTOs, and then transformed into electricity by a centralised generator. These power conduits may be installed in similar manner as described for the cable bus 24.

Operation of interconnected WECs

FIG. 4 shows some interconnected WECs 20 pitching in the waves. The pontoons 21 are able to pitch from side to side because the opposite sides of the pontoons 21 alternatively rest on the crest and the trough of the waves travelling across the lengths of the interconnected WECs 20. The pontoon 21 is made rigid, in order not to bend under the forces of the waves, so that the turning moment of the forces is efficiently transferred to the PTO in the nacelle 22. The diameter of the pontoon 21 is generally designed not to exceed half the wavelength of the waves, so that the pitching angle is a maximum, half a wavelength being the distance between an adjacent crest and trough. At wavelength less than the diameter of the pontoon 21 , the pitching angle is reduced, and less wave energy is extracted. The diameter of the pontoons 21 can measure in the range of a few meters, in order to operate both in waves of those magnitudes and in larger waves. In larger embodiments of the invention, the diameter of the pontoons 21 may measure in the range of 20-50 meters, in order to operate in offshore waves of those magnitudes. An installation of equivalent power capacity may comprise of a greater number of WECs 20 of smaller diameter, or a fewer number of WECs 20 of larger diameter. As the waves at a given installation site would normally vary between a maximum and minimum wavelength, the diameter of the pontoons 21 would be selected based on the most cost effective options, taking into consideration the construction and operation cost of the installation and the total energy that may be harnessed during the life time of that installation.

As shown in FIG. 1 and FIG. 2, all the PTOs of the interconnected WECs 20 are linked by a common cable bus 24. Together, they form a large power generating system of capacity equivalent to the total numbers of interconnected WECs 20 within a given installation. The cable bus 24 is preferably secured on the surface of the WECs 20 and the cable supports 25, as the cable bus 24 may then be easily inspected during routine maintenance. The cable bus 24 should resist wear and tear, as they undergo a large numbers of bending cycles about the coupling devices 23, during the lifetime of the installation. The pontoon 21 would generally carry only a single PTO, secured at the center within the nacelle 22. However several PTOs of small capacity may be secured about the center of pontoon 21 , as a replacement for a single PTO of larger capacity. In other different embodiments of the invention where the wave energy is harnessed in a first stage by PTOs in the form of a compressed fluid, then a network of flexible conduits may collect the compressed fluid from all the PTOs, and then converted into electricity by a common generator. The generator may be installed within one of the WECs 20, or alternatively on a separate floating structure, in an underwater station. In near shore installation, the compressed fluid may even be brought by under water pipes to drive generators located on the shore. Because of the highly variable intensity of the waves, the PTOs would generate electrical energy of highly fluctuating amplitude and frequency, without the use of appropriate power interface within the nacelle 22. The power interface system ensures that the electrical supply from the PTO conforms within certain constant electrical parameter before being connected to the cable bus 24. Power is transferred from the PTOs to the cable bus 24 only at correct calibration of these AC or DC electrical parameters. The power interface system may comprise of diverse power electronic devices such as converters, inverters, rectifiers which are widely used in the wind power systems. The electrical power supply from the PTOs is generally designed to be connected in parallel by the cable bus 24 in a radial configuration, as shown in FIG. 1 and FIG. 2. The cable bus 24 may also be laid according to some other configuration for higher reliability. The ways the PTOs are designed may also influence how they may be electrically connected, in parallel or in series, by the cable bus 24.

The design of the power transmission systems from the interconnected WECs 20 to the main electrical grid on the land would mostly depend on the power capacity of the installation, and the distance from the shore. In small embodiments of the invention as shown in FIG. 1 and FIG. 2, the use of a single underwater transmission cable 26 is most economical. However in larger embodiments of the invention, the power may be transmitted by several separate underwater transmission cables 26, for increased reliability. The connections between the PTOs in the nacelles 22 are then also usually organised in separate clusters and subgroups by several segregated networks of cable bus 24, for still higher reliability. The power for the transmission cable 26 may be tap-off directly at the cable bus 24 and transmitted to shore in the form of direct or alternating current supply (also referred as DC or AC supply). When the power from the cable bus 24 is transmitted over long distances, the DC or AC supply voltage is preferably stepped up by power transformers and appropriate equipment for higher voltage transmission, before connection to the transmission cable 26. The high voltage transmission equipment may be installed within one of the nacelles 22, on a separate floating platform, or in an underwater substation. The power transmission cable 26 may not always be under water. In embodiments of the invention operating very near the shoreline, the power transmission cable 26 may be installed by some aerial means, or some alternate method under specific installation layout conditions. Switchgears for isolation and disconnection of the installation are required for safe and reliable operation of the installation. The cable bus 24 and the transmission cable 26 must be protected from electrical overload. Faulty WECs 20 should be able to be selectively disconnected, in order to allow continued operation of the installation.

Deployment and mooring

Large embodiments of the WEC 20 are generally assembled in dry dock facilities, and then floated. Smaller embodiment of WECs 20 may be factory mounted. The plurality of WECs 20 is then coupled to each other by means of the coupling devices 23, according to pre-layout designs in the calm water of a port, most likely. The cable supports 25 are then fitted where required. The cable bus 24 is later installed between the nacelles 22 and all the PTOs are interconnected. At this stage, the installation may be pre-commissioned and tested before being tugged in the open sea. Upon reaching the site of installation, selected WECs 20 are immediately secured to the mooring line 43 and the system connected to the underwater transmission cable 26. Installations of the mooring systems on the seafloor 45 and the underwater transmission cable 26 have been completed prior to the arrival of the WECs 20. The installation is then ready for final commissioning and exploitation. Embodiments of the invention comprising of very large numbers of WECs 20 may be partly assembled in several segments, and then tugged separately to the operation site, where the segments are then coupled together. An existing installation may be substantially upgraded at a later stage by coupling addition WECs 20, without the need of additional underwater infrastructures, provided the existing mooring systems and the underwater transmission cable 26 have some spare capacity for such expansion. Similarly, installed capacity of an existing installation can be easily downgraded by removal of a number of WECs 20. Embodiments of the invention are generally provided with means for personals to move safely and swiftly between the coupled WECs 20, which is of extreme importance during installation and maintenance work. Protection means for personals would include, provision of anchors, footholds, safety nets, protection rails, where required on the WECs 20. Accommodations for visiting or permanent technical personnel may be provided within larger embodiments of the WECs 20.

Embodiments of the invention are maintained on the ocean surface 35 by a slack mooring system. The slack mooring allows the WECs 20 to heave and pitch without restrain, and also prevent the installation from drifting due to wind and sea currents. The mooring system is designed to resist severe weather condition. As shown in FIG. 1 , only a few selected pontoons 21 are secured by mooring lines 43 to concrete blocks 44 on the seafloor 45. The mooring lines 43 may be directly anchored to the seafloor 45. The mooring lines 43 would comprise of chains, or synthetic ropes. Mooring buoys 46 are attached at the end of the mooring lines 43 in order to facilitate the mooring operation. The moorings lines 43 are spaced relative to each other, so as to prevent the installation from making a complete spin, hence avoiding potential damage to the underwater transmission cable 26 by twisting. The length of mooring lines 43 and the transmission cable 26 should account for seasonal tides variations and height of the waves. The slack in the mooring lines 43 and the transmission cable 26 are prevented from resting on the seafloor 45 by the use of underwater buoys 47. Dragging of the mooring lines 43 and the transmission cable 26 on the seafloor 45, may cause gradual damage to the fauna and the reefs. The use of underwater buoys 47 also reduces possible interference in the operation of the WECs 20, by the weight of the mooring lines 43 and the transmission cable 26. Embodiments of the invention may also be secured to other structures, such as the masts of offshore wind farms and oil rigs. Installation very close to the shoreline may be secured to land based structures. A properly designed mooring system must be carried out by the recommendation and skills of those familiar in the art.

The power take-off (PTO)

The PTO is another important aspect of the embodiments of this invention for efficiently harnessing the wave energy. The pontoons 21 , as they interact with the waves are subjected to various kinds of motions about the flexible coupling device 23. In different embodiments of the invention, PTOs mounted in the nacelles 22 may exploit any of these motions, such as the heaving, the lateral surge motions, or the pitching and rolling motions of the pontoons 21. Energy is harnessed as the pontoon 21 moves in relation to a fix reference connected to the PTO, where the fix reference provides the resistive force to operate the mechanism inside the PTO. In some embodiments of the invention, the fix reference may be provided by a tether lines secure to the seabed and to related components in the PTO. In other embodiments of the invention, the fix reference may be provided by the inertial of a reaction mass, where the reaction mass resists the motion of the pontoons 21. In yet other embodiments of the invention, the fix reference may be provided by a member with a high drag coefficient in water, which resists the motion of the pontoons 21. In preferred embodiments of the invention, the pontoons 21 being coupled by the flexible coupling devices 23 on several sided, would pitch and roll most efficiently, than any other motions induced by the waves. As such, in preferred embodiments of the invention, the PTOs are designed so as to utilize most particularly the pitching and rolling motion of the pontoons 21 about the horizontal plane.

A preferred embodiment of the PTO is shown in FIG. 5 to FIG. 7. The PTO harnesses wave energy as the pontoon 21 pivots about the joints of the coupling devices 23, pitching and rolling about the horizontal plane. This arrangement allows the PTOs to harness energy from waves reaching the connected network of pontoons 21, from any direction. As shown in FIG. 5, the components comprising the PTO are completely enclosed and protected within the body 49 of the nacelle 22. The PTO comprises of a support frame 50 which is firmly secured to the lower section of a support shaft 51. The support shaft 51 is mounted vertically at the symmetrical center of the nacelle 22 on roller bearings 53 and 54, which together with the support frame 50 form a rotatable base. A pair of opposing tapered roller bearings 53 and 54 mounted within a bearing housing 55, allow the rotatable base to endure a large amount of radial and axial forces, during operation of the PTO. The bearing housing 55 may be designed differently with different numbers of bearings and in different arrangements, to fulfill the same purpose. The rotatable base allows components of the PTO to rotate freely about the vertical axis of the support shaft 51 , and to align in any direction within the nacelle 22. As shown in FIG. 6, the bearing housing 55 is firmly secured at the symmetrical center of the nacelle 22 by a support structure, which may comprise of several truss members 56. The side of the nacelle 22 may need to be reinforced about the circumference by appropriate frame structures, such as a number of ring members 57 and lateral struts 58. The spars 27 (not shown in FIG. 5 to FIG. 7) which secure the pontoon 21 to the external side of the nacelle 22, are preferably secured to the ring members 57 so as to reduce mechanical stress to the body 49. In other embodiments of the nacelle 22, the spars 27 may be directly to the sides of the bearing housing 55, rather than to the sides of the nacelle 22. It is understood that the support frame 50 with the ability to rotate about a vertical axis of the nacelle 22, may be constructed in a number of different ways, and which may not always require the need of a centrally mounted support shaft 51 as shown in FIG. 5 to FIG. 7. In these alternative embodiments, the support frame 50 may be mounted on wheels which roll on a peripheral circular rail secured to the ring member 57 of the nacelle 22.

The fix reference, or reference mass for operation of the PTO is provided by a heavy weight 59 inside the nacelle 22. The weight 59 is made from some low cost and dense material, such as concrete. Preferably, a pair of suspension rods 60 is used to secure the weight 59 to either side of the pivot shaft 61 , both mounted on the support frame 50. The suspension rods 60 also significantly off-set the center of gravity of the weight 59 acting on the pivot shaft 61. The pivot shaft 61 is mounted on roller bearings 62 and 63, which allow the weight 59 to hang vertically by the force of gravity, even as the nacelle 22 is pitched sideway as shown in FIG. 7. The roller bearings 62 and 63 are preferably tapered so as to bear significant amount of radial and axial forces during operation. Clearance is provided between the weight 59 and the internal wall of the nacelle 22, to the extent of the maximum pitching angle of the nacelle 22. The need for clearance applies to the internal wall of the nacelle 22 all around the support shaft 51, given that the pivot shaft 61 may be positioned in any direction within the nacelle 22 during operation. The body 49 of the nacelle 22 is shaped so as allow operation of the PTO in normal conditions and at pitching angle most commonly experienced by the pontoon 21. Cushioning bumpers 64 are provided on both sides of the weight 59, in order to prevent any hard contacts with the truss member 56 or the ceiling of the nacelle 22, which may occur in most extreme conditions. The pivot shaft 61 is also symmetrically aligned with the axis of the support shaft 51 , with a balanced lateral weigh distribution, to ensure correct operation of the PTO. In other embodiments of the PTO, the weight 59 together with the suspension rod 60 may be mounted within the support frame 50, in order to allow even more extreme pitching angle of the pontoon 21. The gearbox 65 and the generator 66 are then mounted on the external sides of the support frame 50. In this arrangement, the weigh 59 may be provided with sufficient headroom within the support frame 50, so as to rotate completely about the pivot shaft 61, during most extreme pitching of the nacelle 22. Embodiments of WEC 20 with PTO designed accordingly, may be most useful as standalone units in very rough sea conditions, where during operation the WECs 20 may capsize without disrupting operation.

Energy is harness in the PTO when the longitudinal axis of the pivot shaft 61 is positioned perpendicularly to the travel direction of the ocean waves. Reciprocal movements take place between the suspension rod 60 and the support frame 50, as the nacelle 22 is pitched alternately from side to side. The lateral forces acting on the bearing 53 and 54 are then symmetrically balanced, and the pivot shaft 61 remains perpendicular to the direction of the waves. When the direction of the waves changes and is no longer perpendicular to the axis of the pivot shaft 61, the pitching movement of the nacelle 22 with the waves causes unbalanced lateral reaction forces in the bearing 53 and 54. The support frame 50 would then rotate about the axis of the support shaft 51, until the pivot shaft 61 is repositioned perpendicularly to the direction of the waves. The lateral reaction forces acting on the bearings 53 and 54 are balanced and symmetrical again. The ability for components of the PTO to rotate and align with the wave, while the nacelle 22 maintains a permanent orientation, is an important aspect of the invention. This feature makes it possible for WECs 20 to be couple together, as shown in FIG. 1 and FIG. 2 in large numbers. As the support frame 50 responds almost immediately to the change in wave direction, energy can be harnessed even in choppy irregular waves.

A diverse range of mechanical or hydraulic equipments may be used to convert the slow movements of the articulating joints at the pivot shaft 61 , into high rotational mechanical movement suitable to drive the generator 66. In some embodiments of the nacelle 22, linear generators may be mounted on the support frame 50 and directly coupled to the articulating joint about the pivot shaft 61 by mean of suitable linkage mechanisms. In the embodiment as shown in FIG. 5, the mechanical transmission system comprising of a gearbox 65 is coupled to a rotary generator 66 by a drive shaft 67. Both the gearbox 65 and the generator 66 are firmly secured to the support frame 50. In this embodiment of the PTO, the pivot shaft 61 is also used to drive the input shaft of the gearbox 65 and is hence lock to the suspension rods 60, in order to allow transmission of torque. The gearbox 65 may comprise of several stages of gear trains, including chain drive or belt drive. The pivot shaft 61 or the drive shaft 67 generally includes a clutch mechanism, so that power transmission to the gearbox 65 or the generator 66 may be disconnected during severe weather conditions. In these conditions the nacelle 22 would pitch freely in the waves about the pivot shaft 61 , without causing damage to the mechanical transmission, or overload the generator 66. There is a great flexibility in the design of the mechanical transmission and the way it is connected to the driveshaft 67 of the generator 66. In some other design, the generator 66 may even be secured on the weight 59, with appropriate gears mechanism mounted on both the drive shaft 67 and the support frame 50. An electrical cable 68 connects the generator 66 to the power interface 69 in the equipment room 70, located above the platform or internal deck 71. The support shaft 51 is made hollow or provided with grooves. This allows the passage of the cable 68, and any other cables for control and monitoring purposes, between the support frame 50 and the equipment room 70. A slip ring 72 mounted on the support shaft 51 is required for connection of the cable 68 to the terminals of the power interface 69. The slip ring 72 and the support frame 50 mounted together on the support shaft 51, rotate to a new position every time there is a change in the direction of the waves. Brushless rotary transformers may be used as an alternative to conventional slip rings 72. However conventional slip rings 72 which have a higher current capacity remain a practical choice, as the device is not subjected to intensive use. Additional low power slip rings may be required to connect the cables of any control and monitoring equipment located on the support frame 50.

The equipment room 70 and space above the support frame 50 may accommodate various monitoring and control equipments. Energy storing devices such as batteries, capacitors, flywheels etc, may be installed within the equipment room 70, or any other location of the nacelles 22. Waterproof access traps or doors are provided to allow access inside the nacelle 22 for the purpose of installing equipment and maintenance. In larger embodiments of the invention, the nacelle 22 or other part of the WEC 20 may include storage areas and living space for maintenance crew. Weigh of equipments on the deck 71 also need to be evenly distributed and laterally balanced to ensure flotation stability, and correct operation of the self-alignment mechanism of the PTO. Waterproof cable passages are provided in the equipment room 70 for all electrical cables, such as the cable bus 24, the transmission cable 26, and cables required or any other devices.

The power supply by the generator 66 is highly variable in intensity and frequency. The power interface 69 transforms the supply from the generator 66 into AC or DC power supply with constant parameters which are compatible for electrical connection to the cable bus 24. Only then, the power supply from the power interface 69 can be transmitted into the power network formed by the cable bus 24. Switchgear is provided to disconnect and isolate the power interface 69 automatically during faults or for maintenance purposes. The underwater transmission cable 26 may be connected to the cable bus 24 at the output terminals of the power interfaces 69. For higher voltage transmission to shore, the supply from the cable bus 24 is stepped up before connection to the transmission cable 26. The equipment room 70 may accommodate the power transformer and convertor necessary for stepping up the voltage of the cable bus 24. The power interface 69 can be designed in a number of ways, and would generally comprise of various power electronic equipment such as frequency convertors, frequency invertors, rectifiers, and boosters. The power interface 69 may also be constructed almost entirely of various interconnected electro-machines. The design of the power interface 69 largely depends on the type of generator 66. The generator 66 can be of the permanent magnet type, or the most affordable and reliable induction type. The power interfaces 69 usually rectify the fluctuating supply from the generator 66, before converting it into AC or DC supply, compatible for connection to the cable bus 24. Electrical current is generated (as wave energy is harnessed in the PTO) when the stator and the rotor of the generator 66 rotates relative to each other, under the action of an external forces or torque. As the nacelle 22 is pitched from side to side by the action of the waves, the stator of the generator 66 rotates, forward and backward repeatedly, about the rotor. The induced current in the stator also produces a torque on the rotor, which prevent the relative rotation between the stator and rotor of the generator 66 from taking place. A rotor which is not restrained mechanically by an opposite restraining torque would rotate together with the stator, and no power would be generated by the stator windings of the generator 66.

The restraining torque acting on the rotor of the generator 66, is the result of the sideway displacement 73 of the weight 59 at the end of the suspension rods 60, about the pivot shaft 61, as shown in FIG. 7. The sideway displacement 73 from the vertical axis 74 occurs in the direction of movement 75, as the nacelle 22 is pitched from side to side. The restraining torque is proportional to the amount of the displacement 73 and the mass of the weight 59. The length of the suspension rods 60 and the weight 59 are selected so that the sideway displacement 73 is a minimum for efficient extraction of energy by the PTO. A means to modulate the amount of the restraining torque would allow the WEC 20 to operate in very intense waves without having to shut down completely. The restraining torque can be modulated by the use of a suspension rod 60 of adjustable length, where the length is reduced during intense waves. Similarly the weight 59 may comprise of container fill with seawater, where the amount of liquid can vary, in order to modulate the amount of the restraining torque. The restraining torque may also be modulated electrically by the power interface 69.

The dimension of the nacelle 22 as shown in FIG. 5 to FIG. 7 is mainly determined by the size of the weight 59 and the length of the suspension rod 60. An alternative embodiment of a nacelle 82 is shown in FIG. 8, which allow for greater flexibility in the design of the PTO. The support frame 50 together with the gearbox 65 and the generator 66 are enclosed within a separate lower enclosure 83. The lower enclosure 83 together with the support frame 50 is secured to the support shaft 51. The pivot shaft 61 extends through openings outside the enclosure 83 to secure the pair of externally mounted suspension rods 60 and the weight 59. While the upper enclosure 84 is secured to the pontoon 21 by a number of spars 27, the lower enclosure 83 is free to rotate and align in the direction of the waves. The nacelle 82 allows a great deal of flexibility in the construction of WECs 20 of different power capacity. The nacelle 82 has the ability to accommodate a wide range of weights 59, together with suspension rods 60 of different length, in relation to the power rating of the generator 66. Similarly, the enclosures 83 and 84 may be constructed of standard sizes to accommodate components of PTO for a wide range of power capacity. The weight 59 may be completely submerged below the water surface 35, if constructed of material significantly denser than water. Watertight seals 85 are provided on the support shaft 51 and the pivot shaft 61 to prevent water infiltration inside the different compartments of the nacelle 82. Other alternative means, such as rubber bellows, and barriers may be used to prevent water infiltration.

The preferred embodiments of the nacelles 22 and 82 as disclosed, harness wave energy by means of a PTO comprising of single reciprocating mechanism which rotate a generator 66, wherein the reciprocating mechanism is maintained align in the direction of the incoming waves by an orientation mechanism. In other embodiments of the PTO, the reciprocating mechanism may comprise of a different orientation mechanism, such as a motor or actuator operated by a control system which detect the direction of the waves, and consequently rotate the reciprocating mechanism in the direction of the waves. In embodiments of the invention where the direction of the waves is mostly constant, the PTO may be aligned permanently in a given direction, without the need of an orientation mechanism. In yet other embodiments of the invention, orientation mechanism is not required when the PTO comprises of a plurality of reciprocating mechanisms aligned permanently in different directions, and thus is able to harness incoming waves from all direction. In such alternative designs, the suspension rod 60 with the weight 59 at its lower end may be suspended to an articulating joint, secured at the symmetrical center directly to the truss members 56 within the nacelle 22. As the nacelle 22 would pitch in any direction about the articulating joint, a plurality of compression cylinders disposed and secured around the perimeter of the nacelle 22 may be operated through linkage members connecting the suspension rod 60 to the pistons of the compression cylinders. The compressed fluid from the cylinders may then be transformed at some stage into electrical power. The articulating joint may comprise of universal joints mounted on rotary supports, knuckle joints, or any equivalent means.

WEC comprising of heaving buoys

An embodiment of the invention is shown in FIG. 9 and FIG. 10, comprising of only three set of independent buoys 87. The WEC 86 shown in FIG. 9 and FIG. 10 comprises of nacelle 82. Other embodiment of the WEC 86 may comprise a nacelle 22. The buoys 87 are symmetrically disposed and firmly secured around the nacelle 82 or 22, by independent set of spars 27. Alternative to spars 27, such as a structural platform may also be used to secure the buoys 87 to the nacelle 22 or 82. The pitching movement required to operate the PTO, is the result of the heaving movements of the buoys 87 interconnected by the spars 27. The spars 27 are designed to withstand the load during normal working condition and extreme weather. Additional support frames may be use to reinforce the spars 27. The use of buoys 87, which is more compact, is also more cost effective than fabrication of large floating body of elaborate shape. The use of three set of buoys 87 allows the WEC 86 to harness incoming waves from all direction with a fair degree of symmetry, compared to a perfectly circular floating body in the like of pontoon 21.

The buoys 87 are watertight hollow structures and may be constructed in a number of ways. The buoys 87 may be made of metal or some synthetic material such as fibreglass. Internal or external reinforcement structures may need to be provided for the buoys 87 to withstand the water pressure and to provide support for the coupling devices 23. The buoys 87 may also be constructed of soft inflatable material, such as rubber or some other similar synthetic material. The buoys 87 are generally constructed as spheres which are better able to resist water pressure, or in any other shape most suitable for fabrication. The buoy 87 may comprise of several modular elements assembled together, so that the size may be easily adapted to different power rating of WEC 86, or to facilitate repair. Mooring rings 33 or alternative suitable mooring points are provided on the buoys 87, so that the WEC 86 can be couple to other similar WECs 86 or anchored to the seafloor 45. Mooring point may also be provided at the base of the spars 27 when the buoys 87 are made of material not suitable for such installation.

WECs 86 are coupled together in numbers, in order to form large power generating systems. FIG. 11 shows a few interconnected WECs 86 floating on the ocean surface 35, connected by an underwater transmission cable 26 to the electrical grid on land. The WEC 86 may comprise of nacelle 22 or 82. The WEC 86 are coupled in a similar manner described earlier to couple WECs 20, which allow each of the WECs 86 to heave and pitch independently. The coupling device 23 shown in FIG. 11 comprises of marine fenders 31 , but may be constructed in alternative ways, comprising of various coupling devices and other means. Appropriate cable supports 25 are provided where required for crossing of the cable bus 24 between the WECs 86. Higher numbers of WECs 86 may be secured together in a similar configuration as shown in FIG. 11, or in some other configurations. The cable bus 24 is shown secured on the surface of the spars 27, but may be installed within internal cable ducts provided within the WECs 86. Appropriate numbers of mooring lines 43 and mooring buoys 46 are used to secure the installation to the seafloor 45. The PTOs within larger installations may be connected in separate clusters by several networks of cable bus 24, and with several underwater transmission cables 26 for increased reliability.

A side view of interconnected WECs 86 fitted with nacelle 82 pitching in the waves is shown in FIG. 12. The maximum pitching angle of the WECs 86 occurs when the distance between the buoys 87 is about half the wavelength of the waves. The WEC 86 may be easily optimised for the wave characteristics at a given location by selecting the most suitable length of the spars 27, or the size of the buoys 87. With many buoys 87 heaving in close proximity and also acting as generators of waves, the interference pattern of these waves are difficult to predict in real time. During operation of large numbers of interconnected WECs 86, some of the buoys 87 may experience little or no heaving motion, being in areas of destructive interferences. However the operation of the WECs 86 is not permanently affected, as all the buoys 87 of a particular WEC 86 do not remain together for extended period in an area of destructive interferences, or in a state of synchronised heaving motion. Actually, the dip in power output of a few WECs 86 would be compensated by other WECs 86 within the installation experiencing more intense pitching movements. The constant changing direction of the waves due to the interference has no significant consequences on the power harnessing ability of the WECs 86, as each of the PTOs independently and almost instantly reacts to the changing direction of the waves.

Embodiment of a WEC comprising of a plurality of PTOs

Another embodiment of the invention shown in FIG. 13 is a single WEC 90 comprising of a plurality of PTOs mounted within nacelles 22. Other embodiments of WEC 90 may comprise of nacelles 82, with respective PTOs. The WEC 90 shown in FIG. 13 is equivalent to the layout of interconnected WECs 86 shown in FIG. 11. Both have the same general layout configuration, and the same numbers of PTO within nacelles 22. Other embodiments of WEC 90 may be constructed to different scale, according to different layout configurations, or with different numbers and type of PTOs. In general, embodiments of WEC 90 comprises of a plurality of spars 27 connecting a plurality of flotation buoys ( buoys 87, 91, and 92), and a plurality of PTOs, all permanently assembled together as a single unit, in a manner so that the PTOs can experience independent pitching movements. In any embodiments of the WEC 90, the PTOs need to be firmly secured to at least two separate spars 27, each spar 27 resting on two different buoys so that the heaving motion of the buoys can cause the PTO to pitch from side to side. In order to harness waves from all direction most effectively, the PTOs are supported by three set of spars 27 symmetrically disposed, with each spar 27 resting on a separate buoy, as shown in FIG. 13. A given buoy within the embodiment in FIG. 13 would then accommodate a single, or up to three spars 27, each spar 27 secured to a different PTO.

The size of the buoys within embodiments of WEC 90 varies, depending on the forces acting on them, and which depend on the numbers of spars 27 mounted on them. The size of buoy 87 is designed to support only a single spar 27. The buoy 91 is larger in order to support two set of spars 27, and provides twice as much upthrust compared to buoy 87. The buoy 92 is made even larger as it support three set of spars 27 and provide thrice as much upthrust, compared to buoys 87. The embodiment shown in FIG. 13 comprises of a single larger buoy 92, but other larger embodiments of WEC 90, with different layout of buoys, may comprise of a plurality of buoys 92. It should be noted that the buoy 87 is used only for illustration purposes to appreciate the comparison between embodiments of the invention as shown in FIG. 11 and FIG. 13.

When two or more spars 27 are mounted on a single buoy, a flexible base coupling 93 is used to secure each of the spars 27 to the buoys. The base couplings 93 allow each of the connected spars 27 to move independently from each other, as each of the spars 27 is connected through respective nacelles 22 or 82 to other buoys, which are heaving at different phase and pace relative to each other. This arrangement enable the PTOs mounted in their respective nacelles 22 or 82, to pitch independently from each other. The base couplings 93 may be constructed of various standard couplings devices such as universal couplings, elastomeric couplings, spring couplings, bellow joints, and other similar devices. The base couplings 93 may comprise of custom made mechanical devices or constructed of some soft and flexible material, such as textiles, rubbers, etc.

In large embodiments of the device 90 comprising of a high numbers of buoys (buoys 87, 91, and 92), the spar 27 may include telescopic joint or suitable linkage mechanisms, to allow the length of the spars 27 to stretch or contract freely by some amount. This reduces the damping forces on the heaving movements of the buoys, caused by the buoys themselves pushing upon each other through the connecting spars 27. Cable bus 24 running across the flexible base 93 are installed in appropriate supports to prevent damage and premature wear. The WEC 90 may be coupled to other similar WECs, according to method discussed earlier by the use of coupling devices 23, to form even larger installations.

The invention has been described with reference to certain preferred embodiments thereof. The invention is not limited to these preferred embodiments, and many other variations are possible Embodiments of the invention are also not intended to be limited by the drawings herein, but may be carried with other choice of designs, and methods of construction. The invention may have embodiments within a form which does not provide all the features and benefits set forth, as some of the features may be used or practice separately from others. It should be understood various omission, substitution, and changes in design may be made without departing from the spirit of the invention. The invention is also not limited by construction material. Embodiments of the invention may be constructed with material most suitable to the particular size of the embodiments and the condition of operation. The scope of the invention is indicated by the appended claims rather by the foregoing descriptions.

Claims

CLAIMS The embodiments of the inventions in which an exclusive property or privilege is claimed are as follows:

1. A wave energy harnessing system, comprising:

at least two buoyant bodies;

connecting elements to secure said buoyant bodies adjacent to each other, wherein said buoyant bodies can feely articulate about said connecting element; said buoyant bodies, each comprising at least one power extraction means, wherein said power extraction means is operated by the relative movement of said buoyant body to a reaction mass mounted thereof ; and

a power connection means which connect and combine the energy extracted by said power extraction means mounted on said buoyant bodies.

2. A wave energy harnessing system according to claim 1 , wherein said reaction mass is pivotably mounted to a horizontal pivot shaft secured on said power extraction means.

3. A wave energy harnessing system according to claim 2 wherein said horizontal pivot shaft is rotatably mounted to said buoyant body, such that said horizontal pivot shaft can be positioned perpendicular to the direction of the incoming waves.

4. A wave energy harnessing system according to claim 3, comprising a selforientation mechanism which automatically position said horizontal pivot shaft perpendicular to the direction of the incoming waves.

5. A wave energy harnessing system according to claim 1 , further comprising of support means secured said power connection means between said buoyant bodies.

6. A wave energy harnessing system according to claim 1 , wherein said connecting element comprises of articulating mechanical coupling.

7. A wave energy harnessing system according to claim 1 , wherein said connecting element comprises of marine fenders secured between said buoyant bodies.

8. A wave energy harnessing system according to claim 1 , wherein said connecting element comprises of mooring chains.

9. A wave energy harnessing system according to claim 1 , wherein said connecting element comprises of synthetic ropes.

10. A wave energy harnessing system according to claim 1 , wherein said power extraction means is mounted within said buoyant body.

11. A wave energy harnessing system according to claim 1 , wherein said power extraction means is mounted externally to said buoyant body.

12. A wave energy harnessing system according to claim 1 , wherein said buoyant body is substantially in the form of a circular platform.

13. A wave energy harnessing system according to claim 1 , wherein said buoyant body is in the shape of a ring.

14. A wave energy harnessing system according to claim 13, wherein said power extraction means is secured to said buoyant body by support members.

15. A wave energy harnessing system according to claim 1 , wherein said buoyant body comprises of a plurality of buoyant elements firmly secured around said power extraction means.

16. A wave energy harnessing system according to claim 15, wherein said support member is used to secure each of said buoyant elements to said power extraction means.

17. A wave energy harnessing system according to claim 1 , wherein said power extraction means converts the energy collected from the wave into electrical energy.

18. A wave energy harnessing system according to claim 17, wherein said power connection means comprises of electrical cable which interconnect said power extraction means.

19. A wave energy harnessing system according to claim 1 , wherein the combined I energy collected by said power extraction means is transmitted by at least one power transmission means.

20. A wave energy harnessing system according to claim 17, wherein the combined electrical energy from said power extraction means is transmitted by at least one power transmission cable.

21. A pitching-type wave energy harnessing device for the purpose of extracting energy from incoming waves in any direction, comprising:

a substantially symmetrical buoyant body in the horizontal plane about a central vertical axis;

a support frame rotatably mounted to said buoyant body, wherein said support frame is free to rotate about the vertical axis of said buoyant body; and a power extraction means mounted on said support frame, wherein said power extraction means would aligned in the direction of the waves for maximum power extraction, while said buoyant body maintains substantially a permanent orientation relative to the ocean surface.

22. A pitching-type wave energy harnessing device according to claim 21,

comprising of a horizontal pivot shaft rotabably mounted on said support frame, wherein the axis of said horizontal pivot shaft and the vertical axis of said buoyant body substantially intersect.

23. A pitching-type wave energy harnessing device according to claim 22, wherein said power extraction means comprises of a reaction mass with a low center of gravity mounted to said horizontal shaft, such that the energy is extracted by resisting the relative movement between said reaction mass and said support frame.

24. A pitching-type wave energy harnessing device according to claim 23, wherein the unbalanced lateral and radial forces acting on the bearings supporting said support frame enable rotation of said support frame, such that said horizontal pivot shaft would always align perpendicular to the direction of the waves.

25. A pitching-type wave energy harnessing device according to claim 24, wherein said power extraction means comprises of at least one hydraulic ram operated by the relative movements between said reaction mass and said support frame.

26. A pitching-type wave energy harnessing device according to claim 24, wherein said power extraction means comprises of at least one electrical generator operated by the relative movement between said reaction mass and said support frame.

27. A pitching-type wave energy harnessing device according to claim 24, wherein said horizontal pivot shaft is firmly lock to said reaction mass, thereby causing rotation of said horizontal pivot shaft, when there are relative movements between said reaction mass and said support frame.

28. A pitching-type wave energy harnessing device according to claim 27, wherein a power transmission means is couple to said horizontal pivot shaft to drive a rotating generator.

29. A pitching-type wave energy harnessing device according to claim 26, wherein electrical energy from said electrical generator is transmitted to a power transformation means located on said buoyant body, through rotary electrical connectors.

30. A pitching-type wave energy harnessing device according to claim 29, wherein said power transformation means transforms the power supply from said electrical generator into a usable form of electrical power supply.

31. A pitching-type wave energy harnessing device according to claim 25, wherein energy from said hydraulic ram is transmitted through a rotary hydraulic connecting means to a hydraulic power system located on said buoyant body.

32. A wave energy harnessing device, comprising:

a plurality of buoyant elements disposed at regular interval over an area of the ocean surface in a lattice layout;

a plurality of rigid connecting members, each pivotably coupled to at least two of said buoyant elements, wherein said buoyant elements can heave independently in the waves;

a plurality of power extraction means, each firmly secured to at least one connecting member, wherein the movement of said connecting members enable said power extraction means to harness energy from waves; and

a power connection means interconnecting and combining the power of said power extraction means, wherein said power connection means is installed on said connecting members and said buoyant elements.

33. A wave energy harnessing device according to claim 32, wherein each of said connecting members is secured to at least three of said buoyant elements symmetrically disposed, thereby said connecting member can pitch with relative uniformity in all direction of waves.

34. A wave energy harnessing device according to claim 32, wherein each of said power extraction means comprises an orientation mechanism which align thereof, in relation to the direction of the waves.

35. A wave energy harnessing device according to claim 32, wherein said power extraction means converts useful energy collected from the wave into electrical energy.

36. A wave energy harnessing device according to claim 35, wherein said power connection means comprises of electrical cables which combine the electrical power of said power extraction means.

37. A wave energy harnessing device according to claim 35, wherein the combined electrical energy from said power extraction means is transmitted by at least one power transmission means.

38. A method of deploying a wave energy system comprising a plurality of buoyant bodies, the method comprising:

securing power extraction means on respective buoyant bodies in a port facility; securing plurality of said buoyant bodies together, according to desired layout of said wave energy system, by the use of connecting elements;

installing support means between said buoyant bodies where required;

installing power connection means to link said power extraction means;

securing said power connection means on said buoyant bodies and said support means;

tugging said wave energy extraction system to site of operation;

mooring said wave energy system at site of operation; and

connecting said wave energy system to a power transmission system.

39. A method for expanding the power capacity of an existing wave energy system comprising a plurality of buoyant bodies, the method comprising:

securing power extraction means on respective buoyant bodies in port facility; tugging said buoyant bodies to installation site;

securing said buoyant bodies to existing installation with connecting elements; installing support means to said buoyant bodies;

installing power connection means to link said power extraction means to said existing wave energy system;

adding mooring system to modified wave energy system, if required; and increasing the capacity of the power transmission, if required.