WO2010107316A1

WO2010107316A1 - Aquatic turbine apparatus

Info

Publication number: WO2010107316A1
Application number: PCT/NO2009/000107
Authority: WO
Inventors: Kent Thoressen
Original assignee: Norwegian Ocean Power As
Priority date: 2009-03-20
Filing date: 2009-03-20
Publication date: 2010-09-23

Abstract

There is provided an aquatic turbine apparatus (10, 710, 820) including a rotor (20) coupled to one or more sets of blades (30), a bearing (170, 180, 190) for rotationally supporting the rotor (20) on a support arrangement (40), and an energy pickup arrangement (100, 110) disposed at least in part in the rotor (20) for generating energy when the rotor (20) rotates in operation relative to the support arrangement (40) in response to ocean currents and/or tidal currents acting upon the one or more sets of blades (30). The one or more sets of blades (30) are disposed in a form of a helical-blade rotor, for example a Darrieus-type rotor, operable to extract energy from tidal currents and/or ocean currents irrespective of turbulence and direction of the currents.

Description

AQUATIC TURBINE APPARATUS

Field of the invention

The present invention relates to aquatic turbine apparatus for extracting energy from ocean currents and tidal currents. Moreover, the invention also concerns methods of extracting energy from ocean currents and tidal currents. Furthermore, the invention relates to methods of manufacturing these aquatic turbine apparatus. Additionally, the invention relates to methods of servicing these aquatic turbine apparatus.

Background of the invention

Nacelle-type wind turbines were pioneered by companies such as Vestas AS in Denmark. These turbines are now well known. Each turbine includes a vertical tower mounted at its lower end to ground foundations. A housing is supported at an upper end of the vertical tower. The housing includes a gearbox and generator coupled to a centre-supported propeller-type rotor comprising three aerofoil blades. Incident wind acting upon the blades causes the rotor to rotate relative to the tower and thereby generate mechanical work which is converted into electrical energy at the housing. Although these wind turbines were initially employed on land, they are now increasingly deployed offshore where wind velocity is more favourable for power generation.

Nacelle-type wind turbines need to be continuously controlled for obtaining optimal operating performance. Pitch angles of their blades and pointing directions of their rotor relative to their towers are adjustable for improving performance of the wind turbines in response to changing wind directions and wind speeds. Such functionality renders contemporary nacelle-type wind turbines expensive and complex apparatus requiring frequent servicing.

Georges Jean Marie Darrieus devised a Darrieus-type rotor capable of operating in any wind direction and under adverse weather conditions. The Darrieus-type rotor was originally described in a published United States patent US 1 , 835, 018 published around year 1930. The Darrieus-type rotor is rotationally supported on a vertical axle. However, the Darrieus- type rotor exhibits a pulsatory torque in operation which is undesirable and creates huge momentary bending moments on its rotor blades. In original Darrieus-type rotors, their aerofoil blades were disposed symmetrically on their rotors and had zero rigging angle; "rigging angle" refers to an angle of a plane of the aerofoil blades relative to a central vertical axle to which they are rotationally mounted. When a Darrieus-type rotor is spinning, its aerofoil blades are moving through air in a circular path. An incoming wind is vectorally added to an airflow experienced by a given aerofoil blade resulting in a net force directed obliquely inwards past an axis of rotation of the rotor resulting in a positive net torque to be experienced by the rotor. As the given aerofoil blade rotates towards a rear of the rotor relative to a direction of the incoming wind, its angle of attack changes sign so that a force generated on the given blade is still obliquely in a direction of rotation of the rotor because the aerofoil blades are symmetrical and employ a zero rigging angle. In operation, the Darrieus-type rotor spins at a rate unrelated to a speed of the incoming wind. When the Darrieus-type rotor is stationary, no net rotational force is generated, even if the oncoming wind speed is high, namely a Darrieus-type rotor is not normally self-starting.

A further problem with a Darrieus-type rotor in comparison to a conventional propeller-type rotor is that a majority of mass in the Darrieus-type rotor is disposed in a generally peripheral region of the rotor. In operation, significant centrifugal stresses to the rotor occur, requiring the rotor to be stronger and heavier than a comparable propeller-type rotor. In an overall comparison, Darrieus-type rotors employed in wind turbine apparatus have many disadvantages, especially when such apparatus is designed to generate output power in a MegaWatt (MW) regime.

In a later development, the Darrieous-type rotor is modified so that its blades are canted into a helix, for example three aerofoil blades can be employed which are profiled to have a 60° helical twist. Such a helical feature spreads torque evenly over an entire revolution of the helical Darrieus-type rotor, thereby avoiding generation of undesirable torque pulses in operation.

Water comprises 70% of the Earth's surface and represents an enormous potential source for renewable energy. Professor Alexander Gorlov at Northeastern University in Boston, USA has allegedly devised a rotor for harnessing energy from currents and tides. His early prototypes are based upon the Darrieus-type rotor and are each substantially a metre in diameter and include three helical aquafoil blades. Experimental results have demonstrated that it was possible to extract 35% of energy of water flows through his rotors; this compares highly favorably with a propeller-type rotor which exhibits a corresponding 25% extraction performance. Moreover, Professor Gorlov has envisaged underwater "energy farms" operable to generate electricity from hundreds or even thousands of Darrieus-type helical rotor apparatus electrically coupled to an electricity grid. Professor Gorlov has estimated installed electricity generating facilities based upon such helical Darieus-type rotor technology are likely to cost in a range of $400 to $600 per kiloWatt (kW) of generating capacity; such estimated costs are lower than all other electrical power generating systems presently known. It is estimated that a 5-metre diameter Darrieus-type rotor deployed in an aquatic environment is capable of generating a MegaWatt (MW) of electrical energy when in operation. Aforementioned "energy farms" as envisaged by Professor Gorlov disposed over a region of a few square kilometres are capable of generating as much power as the Chernobyl nuclear reactor complex but without any risk of radioactive pollution and explosion risk. Although aquatic Darrieus-type rotors appear to have enormous potential, relatively little effort has been expended so far to exploit them commercially.

In a published United States patent application no. US 2006/0008351A1 (Belinsky), there are described installations for harvesting energy of river and ocean tidal currents, wherein the installations consist of multiple Darrieus-type rotors equipped with funnels, the funnels being located inline in a river or ocean bottom and orientated perpendicularly to a direction of water movement due to tide or river current. Use of Darrieus-type rotors with associated funnels is alleged to significantly increase efficiency of energy capture from river and ocean currents in comparison to corresponding Darrieus-type rotors devoid of such associated funnels.

In a published international PCT application no. WO 2008/051455 (PCT/US2007/022288) (Ocean Renewable Power Company LLC), there is described a submersible turbine- generator unit including a plurality of Darrieus-type helical turbines mounted to a common shaft with a generator therebetween. The turbines include a plurality of aerofoil-shaped blades mounted transversely to a direction of an incoming fluid flow for rotation in a plane parallel to the fluid flow.

Despite some efforts having been expended to exploit Darrieus-type rotors within ocean and river environments, results so far have been little publicized in comparison to wind turbines. Operating rotors in aquatic environments has many problems associated therewith: corrosion, lack of accessibility for maintenance, crustacean growth, underwater cable connection difficulties. These problems have so far tended to favour alternative approaches to renewable energy systems, for example utilizing offshore wind turbines. Summary of the invention

The present invention seeks to provide a more practical aquatic turbine apparatus for extracting energy from ocean currents, from river currents and tidal currents.

According to a first aspect of the present invention, there is provided an aquatic turbine apparatus as claimed in appended claim 1: there is provided an aquatic turbine apparatus, characterized in that the apparatus includes:

a rotor coupled to one or more sets of blades;

a bearing for rotationally supporting the rotor on a support arrangement; and

an energy pickup arrangement disposed at least in part in the rotor for generating energy when the rotor rotates in operation relative to the support arrangement in response to ocean currents and/or tidal currents acting upon the one or more sets of blades.

The invention is of advantage in that the apparatus provides a simple arrangement for capturing energy present in ocean currents and/or tidal currents.

A benefit provided by the apparatus is that it is capable of operating in slow variable ocean currents and river currents; such operation is rendered possible by employing a relatively large diameter variable-speed generator. As a rule-of-thumb, employing a smaller diameter for the generator requires that the rotor rotates more rapidly for a given amount of output power being produced by the apparatus. Employing a relatively slow speed of rotation for the generator reduces centrifugal forces on the rotor and thereby beneficially assists to reduce stress and wear on the bearing, thereby enabling the apparatus to provide a longer operating life without maintenance.

Optionally, in the aquatic turbine apparatus, the one or more sets of blades are disposed in a form of a helical-blade rotor operable to extract energy from tidal currents and/or ocean currents irrespective of a direction of the currents. The helical-blade rotor is beneficially implemented as a Darrieus-type rotor adapted for use in aquatic environments.

Optionally, in the aquatic turbine apparatus, the energy pickup arrangement is disposed spatially concurrently with the bearing. Such an arrangement provides a compact and simple arrangement which is easier to manufacture and maintain. Optionally, in the aquatic turbine apparatus, the bearing includes interface bearing surfaces defining one or more gaps which are in fluid communication with an aquatic environment of the apparatus when in operation. Such an arrangement thereby avoids a need for fluid-tight seals which are costly and are potentially a cause for unreliability.

Optionally, in the aquatic turbine apparatus, the bearing is implemented in an interface between a glass surface and a flexible polymeric surface. Such an interface is capable of providing an extremely low friction bearing which is robust, simple and capable of withstanding direct exposure to ocean environments, for example corrosive saline solution. More optionally, the flexible polymeric surface is implemented using a halogenated hydrocarbon polymer impregnated into a fabric carrier. Beneficially, rubber is also impregnated into the fabric carrier. Optionally, the fabric carrier is implemented using at least one of: cotton, linen.

The flexible polymeric surface is beneficially implemented as one or more pads which are configured in an "L"-shape orthogonal configuration or a diagonal, for example 45°, configuration. The one or more pads are beneficially mounted in groups of pads, namely arrays of pads, wherein complete arrays can be easily replaced as units when servicing the apparatus, for example such an array includes five pads.

Optionally, the aquatic turbine apparatus includes one or more buoyancy tanks for selectively filling with liquid or gas for raising or lowering the apparatus within its aquatic environment during installation and/or maintenance. Utilization of such buoyancy avoids a need for powerful lifting equipment, for example as required when installing offshore wind turbines which represents a serious problem during installation and maintenance of off-shore wind turbines.

Optionally, the aquatic turbine apparatus includes one or more vanes exhibiting directional response to tidal currents and/or ocean currents received at the apparatus for rendering the apparatus self-starting in respect of turning of the rotor relative to the support arrangement. Such a feature addresses a problem, for example with Darrieus-type rotors, that certain types of rotors are not self starting and/or are subject to stiction effects.

Optionally, in the aquatic turbine apparatus, the energy pickup arrangement is selectively operable to generate an initial starting torque to cause the rotor to rotate from standstill relative to the support arrangement. Such a starting arrangement is useable alone or in combination with other approaches to start the turbine turning from standstill.

Optionally, in relation to the aquatic turbine apparatus, the support arrangement is mounted to a platform via a mounting arrangement, the mounting arrangement being implemented as at least one of:

(a) a single central supporting member;

(b) a pair of planar supporting members;

(c) four equi-spaced non-central supporting members.

Optionally, in the aquatic turbine apparatus, the energy pickup arrangement is encapsulated within the rotor and the support arrangement for isolating it from an aquatic environment of the apparatus when in operation. Such encapsulation reduces degradation and corrosion that would otherwise arise if the energy pickup arrangement were exposed directly to ocean saline water.

Optionally, the aquatic turbine apparatus includes a connection gathering arrangement for managing a connection to the apparatus when the apparatus is raised and/or lowered within its aquatic environment during installation and/or maintenance.

According to a second aspect of the invention, there is provided an energy system as defined in appended claim 13: there is provided an energy system including a plurality of apparatus pursuant to the first aspect of the invention. Such energy systems are also known as "energy farms" and beneficially comprise many hundreds or even thousands of apparatus spatially disposed in an array in an aquatic environment subject to tidal currents and/or ocean currents.

Optionally, in the energy system, the apparatus include associated rotors which are operable to rotate in mutually different directions for ensuring that the system experiences negligible overall torque when in operation.

According to a third aspect of the invention, there is provided an aquatic vessel as claimed in appended claim 15: there is provided an aquatic vessel including a gripping and guiding arrangement mounted thereto, the gripping and guiding arrangement being adapted to engage to one or more features of the apparatus pursuant to the first aspect of the invention, the arrangement being operable to raise or lower the apparatus whilst maintaining the apparatus in a constant angular orientation. Optionally, in relation to the aquatic vessel, the gripping and guiding arrangement is operable to guide the apparatus within a plane of movement, the plane being substantially vertical and intersecting a longitudinal axis of a hull of the vessel for reducing a tendency for the vessel to roll when the gripping and guiding arrangement is operable to raise or lower the apparatus.

According to a fourth aspect of the invention, there is provided a method of raising an apparatus pursuant to the first aspect of the invention, the method being defined in appended claim 17: there is provided a method of raising an apparatus pursuant to the first aspect of the invention, the method using an aquatic vessel pursuant to the third aspect of the invention, the method including;

(a) engaging a gripping and guiding arrangement mounted to the vessel onto one or more features of the apparatus;

(b) filling one or more buoyancy tanks of at least one of the gripping and guiding arrangement and the apparatus with a gas for increasing buoyancy to generate a buoyant lifting force on the apparatus; and

(c) guiding the apparatus through its aquatic environment whilst the buoyant lifting force raises the apparatus to an upper surface of its aquatic environment.

According to a fifth aspect of the invention, there is provided a method of lowering an apparatus pursuant to the first aspect of the invention, the method being defined in appended claim 18: there is provided a method of lowering an apparatus pursuant to the first aspect of the invention, the method using an aquatic vessel pursuant to the third aspect of the invention, the method including: (a) engaging a gripping and guiding arrangement mounted to the vessel onto one or more features of the apparatus;

(b) filling one or more buoyancy tanks of at least one of the gripping and guiding arrangement and the apparatus with a liquid for decreasing buoyancy to generate a downward force on the apparatus; and (c) guiding the apparatus through its aquatic environment whilst the downward force lowers the apparatus into its aquatic environment.

According to a sixth aspect of the invention, there is provided an aquatic turbine apparatus as claimed in appended claim 19: there is provided an aquatic turbine apparatus including:

a rotor coupled to one or more sets of blades, a bearing for rotationally supporting the rotor on a support arrangement, and

an energy pickup arrangement for generating energy when the rotor rotates in operation relative to the support arrangement in response to ocean currents and/or tidal currents acting upon the one or more sets of blades, wherein the bearing is implemented in an interface between a glass surface and a flexible polymeric surface.

Optionally, in the aquatic turbine apparatus, the bearing includes interface bearing surfaces defining one or more gaps which are in fluid communication with an aquatic environment of the apparatus when in operation.

According to a seventh aspect of the invention, there is provided an aquatic bearing as claimed in appended claim 21 : there is provided an aquatic bearing for providing a rotational bearing interface between a first component and a second component for enabling the first component to rotate relative to the second component in operation, wherein the bearing is implemented in an interface between a glass surface and a flexible polymeric surface coupled to the components.

Optionally, in the aquatic bearing, the bearing includes interface bearing surfaces defining one or more gaps which are in fluid communication with an aquatic environment of the bearing.

It will be appreciated that features of the invention are susceptible to being combined in any combination without departing from the scope of the invention.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

FIG. 1 is a schematic illustration of an embodiment of an aquatic turbine apparatus pursuant to the present invention, wherein the apparatus utilizes a Darrieus- type rotor rotationally mounted upon a bearing arrangement supported on a single vertical central support member;

FIG. 2a is a perspective exterior view of the aquatic turbine apparatus of FIG. 1 ; FIG. 2b and FIG. 2c are cross-sectional views of a blade for use in the apparatus of FIG. 2a;

FIG. 3 is an alternative embodiment of an aquatic turbine apparatus pursuant to the present invention, wherein the apparatus utilizes a Darrieus-type rotor rotationally mounted upon a bearing arrangement supported on a horizontal central support member;

FIG. 4a is a schematic illustration of an implementation of bearing surfaces employed in the aquatic turbine apparatus pursuant to the present invention;

FIG. 4b and FIG. 4c are schematic illustrations of implementations of bearing pads employed in an apparatus pursuant to the present invention;

FIG. 5a and FIG. 5b are schematic illustrations of an aquatic turbine apparatus pursuant to the present invention being raised from a river or ocean floor for installation or maintenance purposes;

FIG. 6 is an illustration of an aquatic vessel adapted for installing and servicing aquatic turbine apparatus pursuant to the present invention;

FIG. 7a and FlG. 7b are illustrations of the vessel of FIG. 6 raising an aquatic turbine apparatus pursuant to the present invention;

FIG. 8 is a schematic illustration of a submerged floating system incorporating one or more aquatic turbine apparatus pursuant to the present invention, wherein each apparatus is supported on two substantially planar cross-section support members;

FIG. 9 is an enlarged illustration of an aquatic turbine apparatus pursuant to the present invention wherein the apparatus includes two substantially planar cross-section support members, the aquatic turbine apparatus being used for example in the system of FIG. 8;

FIG. 10 is an alternative submerged system including one or more aquatic turbine apparatus pursuant to the present invention, wherein each apparatus is supported by four equi-distant support members; and FIG. 11 is an embodiment of an aquatic turbine apparatus pursuant to the present invention, wherein the aquatic turbine apparatus is supported by four equidistant support members.

In the accompanying diagram, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non- underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

Description of embodiments of the invention

In a published international PCT patent application no. WO2008/051455 (PCT/US2007/022288) submitted by Ocean Renewable Power Company, the content of the patent application hereby being incorporated by reference, diagrams are presented showing ocean currents and tidal currents at various geographical locations throughout the World. For example, the Gulf Stream transports continuously enormous quantities of water from equatorial regions towards the North Pole which assists to cool the equatorial regions and warm Northern regions. Even extracting a small portion of kinetic energy present in these ocean currents is more than sufficient to meet present human electrical energy requirements without significant pollution or environmental degradation occurring. However, to be economically viable, systems for extracting energy from tidal currents and ocean currents have to be operable to generate power at a cost which is at least comparable to, and preferably less than, alternative contemporary energy systems such a coal-fired power stations, oil-fired power stations, gas-fired power stations, nuclear power stations and hydroelectric power plants.

For reducing cost, energy systems for extracting tidal and ocean currents beneficially employ a plurality of apparatus which are manufactured in large numbers. Moreover, the apparatus is beneficially easy to service, highly reliable and capable of being refurbished and re-used to reduce waste. Earlier proposals for submerged apparatus for extracting energy from ocean currents and tidal currents have been too complex or insufficiently efficient to provide viable alternatives to known contemporary energy systems as elucidated above. The inventor has sought, in devising the present invention, to address a problem of providing an aquatic turbine apparatus which fulfils requirements for economically viably extracting energy from ocean currents and tidal currents to provide useful energy for human society. The useful energy is optionally in the form of electrical power. Alternatively, the useful energy can be provided via other energy carriers, for example hydrogen gas and energy- conveying chemical compounds such as hydrocarbons generated from commonly occurring compounds such as carbon dioxide and water.

In FIG. 1 and FIG. 2a, there is shown an aquatic turbine apparatus indicated generally by 10. The apparatus 10 utilizes a Darrieus-type rotor 20 implemented as a peripheral ring-shaped member. Two sets of three helical blades 30 are attached at their first ends to the rotor 20; second ends of the blades 30 are unattached as illustrated. Optionally, the rotor 20 has at least one set of blades 30. Optionally, each set includes three blades 30 although other numbers of blades 30 in each set are feasible. The blades 30 have a helical formation for avoiding torque pulses being generated in operation. Moreover, the blades 30 are beneficially mounted in an equi-distant manner onto the rotor 20 as illustrated for obtained a non-eccentric distribution of mass for the rotor 20. The blades 30 are manufactured from composite material, for example a combination of carbon fibre and/or fibre-glass bonding by one or more resin adhesives, so that they are capable of remaining structurally strong even after many years of being submerged in saline ocean water.

The peripheral ring-shaped member of the rotor 20 is beneficially manufactured from composite material. For example, the rotor 20 is optionally manufactured from synthetic rubber and/or natural vulcanized rubber. Beneficially, the composite material is reinforced with one or more structural members, for example one or more ring-shaped structural strengthening components. Moreover, the rotor 20 is beneficially provided with detachable mounts for receiving one or more bearing pads. For coping with considerable forces experienced by the blades 30 in operation, the blades 30 are beneficially attached to the one or more ring-shaped structural strengthening components encapsulated within the rotor 20.

Other types of rotor other than a Darrieus-type rotor can optionally be employed for implementing the rotor 20. For example, a rotor with pivoting or flexurally-bending vanes can be employed, wherein the vanes are pivotally pushed outwardly by a water current from which energy is to be extracted when the vanes are rotating in a direction with the water current, and are pivotally pushed inwardly by the water current when the vanes are rotating in a direction against the water current. Beneficially, such vanes are fabricated from polypropylene material which is inert to corrosion from ocean water, inexpensive and able to elastically flex many million of times before work hardening.

The rotor 20 is rotationally mounted onto a central bearing member 40 via a bearing surface which will be described in more detail later. The central bearing member 40 is beneficially fabricated from composite material so that it is capable of remaining structurally strong and waterproof, even after many yeas of submersion in aquatic environments. Alternatively, the central bearing member 40 is fabricated from closed-pore concrete including fine micron- sized silica particles for rendering the concrete impervious to ingress from ocean water. Moreover, the central bearing member 40 is supported at its centre via a first end of a single central support member 50. In FIG. 1, the support member 50 is substantially vertical in operation, although an alternative horizontal configuration of the support member 50 as illustrated in FIG. 3 and indicated by 200 is also feasible within the scope of the present invention. Intermediate angles between vertical and horizontal for the support member 50 are also feasible. A second end of the support member 50 is coupled to a foundation member 60 which beneficially houses energy processing equipment 70 for processing energy generated in operation by the rotor 20 in cooperation with the central bearing member 40. Optionally, the foundation member 60, the support member 50 and the central bearing member 40 are a unitary item. Optionally, at least a portion of the processing equipment 70 is housed within the bearing member 40. The foundation member 60 is beneficially fabricated from closed-pore concrete, for example concrete including micron-sized silica particles for rendering the concrete impervious to ocean water. Moreover, the foundation member 60 is beneficially relatively heavy, for example 50 tonnes or more in weight, and planar for resisting lateral forces experienced by the rotor 20 when acted upon by ocean and/or tidal currents. The foundation member 60 is capable of engaging onto uneven ocean beds or river beds without adversely affecting operation of the apparatus 10; for example, the apparatus 10 can be titled 15° from vertical deployment and yet operate satisfactory; such an error of orientation would be seriously detrimental to the operation of a conventional nacelle- type wind turbine. The apparatus 10 further includes a connecting arrangement 80 through which energy generated by the apparatus 10 is conveyed away from the apparatus 10 when in operation. The connecting arrangement 80 is beneficially implemented as an armoured flexible elongate component including at least one of: electrical cables, optical fibres, pipes. Additionally, the foundation member 60 optionally includes one or more floatation tanks 90 which can be selectively filled in operation with water or air when raising the apparatus 10 from an ocean bed, or for lowering the apparatus 10 onto the ocean bed. Beneficially, the rotor 20 has an outside diameter in a range of 5 to 50 metres, more preferably in a range of 7 to 30 metres. Rotor diameters in excess of 50 metres tend to be awkward and difficult to transport and manipulate, whereas rotor diameters of less then 5 metres tend to generate insufficient power to be highly commercially viable. The blades 30 beneficially have a length is a range of 5 to 50 metres, and have a fixed cross sectional area over its entire length or a cross-sectional area which progressively increases from remote end tips of the blades 30 to a region at the rotor 20 whereat the blades 30 are jointed to the rotor 20. Each blade 30 beneficially has a cross section as illustrated in FIG. 2b or FIG. 2c wherein a width of the blade 30 in a direction A - A is in a range 10 cm to 120 cm, and a thickness is a direction B - B in a range of 0 cm to 50 cm. Optionally, the blades 30 are fashioned to have an aerofoil cross-sectional profile as shown in FIG. 2c; optionally, the aerofoil cross-sectional profile is symmetrical about the axis B - B; alternatively, the airfoil cross-sectional profile is asymmetrical about the axis B - B. Optionally, the blades 30 are provided with a substantially constant cross-section along their entire length.

A direct electro-magnetic induction energy extraction arrangement is provided in a spatial region near the bearing surface, for example as illustrated. The energy extraction arrangement includes a configuration of powerful permanent magnets 100 disposed around the ring-shaped member of the rotor 20. The permanent magnets 100 are encapsulated within the material employed to fabricate the rotor 20 to prevent ocean water degrading the magnets 100. Beneficially, the magnets 100 are neodymium rare-earth magnets, although other types of permanent magnets may be optionally employed. Moreover, the magnets 100 are beneficially disposed in an equi-spaced manner around the ring-shaped member of the rotor 20 in an alternating manner of polarity and are orientated to project their magnetic fields towards the central bearing member 40. The central bearing member 40 is provided with one or more electrical coils 110, optionally wound around laminated or multi-strand ferromagnetic material cores for efficiently guiding magnetic fields generated by the magnets 100 to couple into the one or more coils 110. The one or more coils 110 are disposed along a peripheral edge of the bearing member 40 to be in close proximity to the magnets 100 when the apparatus 10 is in operation so that magnetic fields generated by the magnets 100 are coupled efficiently to the one or more coils 110. The one or more coils 110 are beneficially disposed in an equi-spaced manner around the bearing member 40. Moreover, the one or more coils 110 are beneficially encapsulated within the bearing member 40 for protecting them from degradation due to saline ocean water.

The one or more coils 110 are coupled to the processing equipment 70. Movement of the magnets 100 relative to the coils 110 when the rotor 20 rotates in response to ocean and/or tidal current acting upon its blades 30 generates electromotive force (e.m.f.) corresponding to generated electrical power which is provided to the processing equipment 70. Subsequently, the processing equipment 70 supplies the power via the connecting arrangement 80, for example for supplying electrical power to an electrical grid on a land region. The processing equipment 70 optionally includes pulse width modulated (PWM) electrical power conversion devices for converting varying electromotive force (e.m.f.) generated at the one or more coils 110 into electrical output power signals suitable for feeding via the connecting arrangement 80 onto an electricity grid. However, the processing equipment 70 is susceptible to being implemented in other manners, for example water can be decomposed by electrolytic action at the processing equipment 70 to generate hydrogen gas which is subsequently conveyed via the connecting arrangement 80 to land, for example for providing hydrogen for use in hydrogen fuel-cell vehicles. Yet alternative, the processing equipment 70 can be provided with raw materials of hydrogen and carbon dioxide, and use power generated by the one or more coils 110 in a catalytic device of the equipment 70 to convert the raw materials to generate hydrocarbon fuel for conveying via the connecting arrangement 80 to land. Yet other implementations are possible for the processing equipment 70, for example electrical power generated in operation by the apparatus 10 is conducted on-shore and the processing equipment 70 for receiving the electrical power is also located on-shore.

Occasionally, for example after many years of operation in an aquatic ocean environment, the aquatic turbine apparatus 10 needs to be raised from its aquatic environment to an ocean upper surface for inspection, repair and/or upgrading. The foundation member 60 is therefore beneficially provided with one or more features 150, for example one or more recesses, to which a lifting tool can be engaged for manipulating the turbine apparatus 10.

A Darrieus-type turbine is known not to be self-starting. In order to assist the apparatus 10 to spontaneously start rotating when subject to ocean currents or tidal currents, an outside peripheral edge of the rotor 20 is provided with one or more vane-like features 160 for causing directionally-dependent resistance to water flow thereacross and thereby generate a relatively small starting torque for initially rotating the rotor 20. Alternatively, or additionally, the one or more coils 110 can momentarily be energized in a specific sequence so that the rotor 20 functions as a stator of stepper motor to be spun into rotation; once the rotor 20 is rotating, energizing the one or more coils 110 can be terminated and the coils 110 then employed to generate electrical power for the processing equipment 70.

The rotor 20 with its blades 30 is rotationally supported at a peripheral of the central bearing member 40 as illustrated in FIG. 1. Such rotational support is beneficially provided by employing two ring-shaped members 170 mounted onto upper and lower peripheral edges of the bearing member 40, such that the ring-shaped member 170 presents bearing surfaces towards the rotor 20 for restraining movement of the rotor 20 in lateral and vertical directions, but nevertheless allowing for the rotor 20 to rotate. The ring-shaped member 170 is beneficially fabricated as a single integral component, for example as a cast component. Beneficially, each ring-shaped member 170 is manufactured from an inert hard material, for example from amorphous silica glass material or silicon nitride material. Moreover, an inner divide and removable recess of the rotor 20 formed to match the bearing member 40 is provided with pads 180,190 for slidably abutting onto the ring-shaped members 170 and restraining the rotor 20 in lateral and vertical directions respectively. As illustrated in FIG. 4a, the pads 180 are provided with gaps 210 therebetween for enabling ocean water to penetrate continuously to a clearance gap 220 formed between the ring-shaped member 170 and an abutting surface of the pads 180. Similar considerations pertain for the pads 190. The apparatus 10 thus employs ocean water as a lubricant for ensuring low-friction rotation of the rotor 20 relative to the bearing member 40 in operation. Such an approach avoids a need for seals to exclude ocean water and thereby reduces cost of the apparatus 10. Moreover, such an approach also avoids a need for using any type of additional lubricant which may be potentially harmful to biota in an ocean environment. It is desirable that the clearance gap 220 be continuously supplied with fresh ocean water to avoid frictional losses causing water in the clearance gap 220 to evaporate to form steam bubbles rendering the clearance gap thereby devoid of lubricant. The clearance gap 220 is beneficially less than 100 μm wide, and preferably less than 50 μm wide. Such a small size of the clearance gap 220 prevents ingress of contaminants that could otherwise erode the exposed bearing surfaces of the ring-shaped members 170.

The pads 180, 190 are beneficially fabricated from a flexible polymer material, for example rubber material. The flexible polymer material is preferable impregnated with one or more friction-reducing materials, for example one or more of: a hydrocarbon polymer, a halogenated hydrocarbon polymer, a fluorinated hydrocarbon polymer (for example PTFE or similar), a fabric such as cotton or linen, friction-reducing nanoparticles. "PTFE" is an abbreviation for polytetrafluoroethylene. For example, the pads 180, 190 can be manufactured from cotton and/or linen (flaks) fabric pads which are pressure impregnated with rubber and friction-reducing additives. Optionally, the apparatus 10 can be alternatively implemented so that ring-shaped members 170 are mounted to the rotor 20 and the pads 180, 190 are mounted to the bearing member 40. Optionally, the pads 180, 190 are implemented in detachable arrays, wherein each array includes a plurality of pads. The pads 180, 190 are shown implemented in an orthogonal manner in FIG. 1 and FIG. 4b. Optionally, the pads 180, 190 are disposed is a non-orthogonal manner, for example in a 45° manner as illustrated in FIG. 4c for rotatably retaining the rotor 20 in vertical and horizontal directions; in the example of FIG. 4c, the ring-shaped member 170 is ground and polished to present a frusto-conical surface to the pads 180, 190. Optionally in FIG. 4c, only a single row of pads is employed around the ring-shaped member 170.

The ring-shaped members 170 require careful manufacture and functionally must provide smooth bearing surfaces for interfacing to the pads 180, 190. Glass is a highly beneficial material to employ for the members 170 because:

(a) it is abundantly available - silica is a commonly occurring compound in nature;

(b) it is not degrading by corrosion when exposed to ocean water;

(c) it is an amorphous material and therefore is devoid of micro-crystals which could otherwise become dislodged by wear to cause surface roughness which could aggravate further wear;

(d) it is dimensionally stable and strong;

(e) it can be cast as large-sized components, for example as in mirrors for astronomical reflecting telescopes;

(f) is can be machined by grinding and polishing processes to high precision; and (g) it is non-toxic to an ocean environment.

Moreover, glass is a relative hard material in comparison to a hardness of material employed by the pads 180, 190. Correspondingly, in operation, the pads 180, 190 tend to polish bearing surfaces of the glass material of the ring-shaped members 170 which further reduces friction at the clearance gap 220 in operation.

Each ring-shaped member 170 can have a diameter in a range of 3 to 50 metres and have a cross-section dimension in a range of approximately 10 cm x 10 cm to 50 cm x 50 cm.

Moreover, bearing surfaces of the members 170 are beneficially manufactured to be circular to within a tolerance error of less than 1 mm, preferably to be circular to within a tolerance error of less than 100 μm, and most preferably to be circular to within a tolerance error of less than 10 μm. In. order to achieve such tight tolerances, the following manufacturing method is beneficially employed including:

(i) heating a quantity of silica glass to a molten state, for example using a gas-fired oven;

(ii) preheating a casting mould to an elevated temperature of several hundred degrees centigrade;

(iii) pouring the molten glass into the mould; (iv) allowing the mould and its molten glass gradually to cool down in a substantially isothermal manner to prevent the glass material becoming stressed, thereby forming a solid glass ring casting;

(v) coarse grinding the ring casting to form bearing surfaces for the pads 180, 190; (vi) allowing the ground ring casting to attain an iso-thermal state;

(vii) fine grinding the bearing surfaces of the ring casting whilst using copious quantities of cooling fluid pre-heated to an iso-thermal temperature of the ground ring casting; and (viii) precision polishing the bearing surfaces using progressively finer grades of diamond abrasive until the bearing surfaces assume a mirror-like finish, namely surface irregularities are less than circa 0.5 μm, namely approximately the wavelength of humanly visible light.

As the rotor 20 rotates in operation, the members 170 become increasingly polished. The gap 220 is beneficially sufficiently small to prevent foreign particulate contamination from becoming embedded in the pads 180, 190. Eventually, the pads 180, 190 become worn out and need to be replaced. Optionally, the rotor 20 includes a mechanism for slowly advancing the pads 180, 190 as they become worn, for example a backing layer to the pads 180, 190 which slowly expands as it becomes hydrated after being many years submerged in ocean water. Such a refinement feature is beneficially incorporated into the apparatus 10 for reducing a need for servicing and maintaining the apparatus 10.

In FIG. 5a and FIG. 5b, the connecting arrangement 80 is beneficially disposed in a spiral configuration indicated by 260 on a spring-like bearing component, for example in a manner of a toy "slinky spring". The bearing component is beneficially implemented as a slack helical spring whose windings are planar in cross-section with a greatest cross-sectional dimension in a horizontal direction so that the bearing component is readily extended in a vertical direction but resists deflection in a horizontal direction. Optionally, the spiral configuration 260 is provided with an open-top walled container 250 for retaining the connecting arrangement 80. Optionally, the container 250 is outwardly tapered from bottom to top thereof to assist guiding the connecting arrangement 80 into the container 250.

A lifting tool 300 coupled to an ocean vessel can be engaged into the one or more recesses 150 of the foundation member 60 for raising the apparatus 10 to an upper surface of the ocean, for example for inspection, servicing and/or repair. As the apparatus 10 is lifted up, namely raised, the connecting arrangement 80 and its bearing component extend to yield slack length. Such a characteristic avoids disturbing facilities, for example a junction box deposed on an ocean bed 270 coupled to receive power form several apparatus 10 disposed in a constellation together upon the ocean bed 270, as the apparatus 10 is raised and then subsequently lowered again onto the ocean bed 270.

In FIG. 6, an aquatic vessel for servicing the apparatus 10 is indicated generally by 600. The vessel 600 includes a hull 610 supporting a bridge 620. The vessel 600 includes a forward portion which is equipped with one or more anchors 630 for anchoring the vessel 600 when in operation to hold a given position. Optionally, the vessel 600 is also provided with dynamic anchoring arrangements utilizing GPS, an inertial navigation unit and magnetic compass and/or gyro-compass for controlling one or more engines and associated one or more propellers or water jets of the vessel 600 for maintaining its position and orientation during operation. Port side and star board portions of the vessel 600 are beneficially of standard construction. A manipulation apparatus 660 with associated arms is mounted to a platform 650 at a rear aft portion of the vessel 600. The vessel 600 has a substantially horizontal longitudinal axis, and is capable of bearing considerable weight at its rear aft portion without risk of rolling or tipping, provided that the manipulation apparatus 660 holds its load in a vertical plane intersecting the longitudinal axis of the vessel 600.

Referring next to FIG. 7a and FIG. 7b, the manipulation apparatus 660 comprises a grabber assembly 670 including the aforementioned lifting tool 300 illustrated in FIG. 5b. The grabber assembly 670 is coupled via two parallel arms 680a, 680b which are of mutually similar length. Ends of the parallel arms 680a, 680b are pivotally coupled to the platform 650 and to the grabber assembly 670 as illustrated. The arms 680a, 690b are beneficially fabricated from aluminium and/or composite material with voids and/or holes centrally therein for reducing their weight. Moreover, the grabber assembly 670 is optionally itself equipped with one or more floatation tanks 695 which can be selectively filled with air or other gas when raising the apparatus 10, and selectively filled with water or other liquid when lowering the apparatus 10 towards the ocean bed 270. Use of the one or more floatation tanks 695 is of benefit in that it potentially avoids a need to include the one or more floatation tanks 90 within each apparatus 10, thereby reducing cost and complexity of the apparatus 10; one vessel 600 is capable of servicing many apparatus 10 in a sequential manner. Beneficially, both the apparatus 10 and the grabber assembly 670 are provided with one or more floatation tanks 90, 695 respectively for reducing an amount of stress experience by the lifting tool 300 when in operation manipulating the apparatus 10. Moreover, when not coupled to an apparatus 10, the one or more floatation tanks 695 of the grabber assembly 670 enable the assembly 670 to be raised from the ocean bed 270 to enable the vessel 600 to move from one apparatus 10 to another. During maintenance or servicing, the apparatus 10 can be raised from the ocean bed 270 by employing a swinging motion 690 of the parallel arms 680a, 680b by invoking a method involving:

(a) engaging the tool 300 into the one or more features 150 of the apparatus 10; (b) progressively displacing water or other liquid in the one or more tanks 90 of the apparatus 10 to provide the apparatus 10 with buoyancy; and (c) using the arms 680a, 680b to guide the apparatus 10 as it floats up to an upper surface of the ocean.

When the apparatus 10 is at the upper surface of the ocean, it can be winched onboard an ocean vessel and/or can be serviced whilst floating at the ocean surface. Beneficially, the tool 300 is equipped with one or more cameras and floodlights for inspecting the apparatus 10 whilst it is being prepared to be raised to the upper surface of the ocean.

During installation and/or after servicing, the apparatus 10 can be lowered from the ocean upper surface to the ocean bed 270 by employing the swinging motion 690 of the parallel arms 680a, 680b by employing a method involving:

(a) engaging the tool 300 into the one or more features 150 of the apparatus 10;

(b) progressively filling the one or more tanks 90 of the apparatus 10 with water or other liquid to reduce a buoyancy of the apparatus 10; and (c) using the arms 680a, 680b to guide the apparatus 10 as it sinks to the ocean bed

270.

Optionally, when utilized, the one or more tanks 695 of the grabber assembly 670 can be progressively filled with water to lower the apparatus 10 to the ocean bed 270.

It is envisaged that the apparatus 10 will need to be serviced only occasionally, for example once each ten years, such that the vessel 600 is capable of servicing a very large number of apparatus 10 over a ten-year period, for example several thousand apparatus 10. Such servicing optionally, for example, involves replacing the pads 180, 190. Apart from the pads 180, 190, the apparatus 10 comprises component parts which are unlikely to wear out. For this reason, the apparatus 10 is envisaged to have an operating lifetime of many decades of years, for example in a range of fifty to one hundred years. When the apparatus 10 is designed to have its rotor 20 with a diameter in a range of 10 to 20 metres, the apparatus 10 is capable of generating several MegaWatts (MW) of power; at present electricity production costs in relation to the cost of manufacturing the apparatus 10 and also its operating longevity, not only is the apparatus 10 capable of recovering its production cost very rapidly, but also over a longer period represents a least expensive manner of generating electricity. Such benefit is provided without risk of explosion (e.g. in contradistinction to a major explosion as occurred at Chernobyl), without generating dangerous or toxic waste during its manufacture, deployment and operation (e.g. in contradistinction toxic wastes are generated when operating nuclear and fossil-fuel burning power plants), without disfiguring landscapes (e.g. in contradistinction to wind turbines and hydroelectric schemes which cause disfigurement to landscapes), without representing any noise irritation (e.g. in contradistinction to wind turbines which generate noise pollution when in operation). Moreover, when located on the ocean bed 270, the apparatus 10 is well protected from adverse weather conditions, for example hurricanes, floods and storms which can damage wind turbines and hydroelectric schemes. Moreover, on account of the apparatus 10 being employed in large numbers in energy farms, failure of any given apparatus 10 does not endanger overall energy production or security from the energy farms; a probability of all apparatus 10 in an energy farm failing simultaneously is relatively low. Furthermore, on account of ocean and tidal currents being predictable and sustainable, the apparatus 10 is able to provide a reliable and predictable source of energy in juxtaposition to wind turbines whose power output can be highly variable depending upon weather conditions. Unlike a conventional nacelle-type wind turbine, the apparatus 10 does not include any gearbox which can potentially wear out and cause such wind turbines to be unreliable in use. Moreover, the apparatus 10 potentially uses less material in its manufacture than a conventional wind turbine which weighs in an order of 200 to 400 tonnes and employs a 50 tonne foundation.

Referring to FIG. 8 and FIG. 9, there is shown an energy production system indicated generally by 700. The system 700 employs one or more apparatus 710. Each apparatus 710 is derived from the aforementioned apparatus 10, namely includes the rotor 20 with its associated blades 30 in combination with the central bearing member 40. In the system 700, the one or more apparatus 710 are each supported via a "V"-shaped member comprising two arms 730 which are relatively planar in cross-section. Longitudinal cross-sectional axes X-X of the arms 730 are beneficially mutually parallel as illustrated in FIG. 9 in plan view for enabling the "V"-shaped member to most effectively resist turning torque occurring at the central bearing member 40 operating in combination with the rotor 20 and its associated blades 30. Use of two arms 730, namely an even number, in combination with three blades 30 on each of upper and lower portions of the rotor 20 avoids torque pulses and interaction between the blades 30 and arms 730. Beneficially, the "V"-shaped member comprising the arms 730 can be implemented to function as a type of wing for providing the apparatus 710 with an upwardly-directed buoyancy force when ocean currents or river currents flow past the arms 730. The apparatus 710 is thereby capable of being selectively elevated within an ocean or river when in operation. The arms 730 implemented to function as wings are beneficially optionally implemented as a single unitary component. The system 700 further comprises a platform 720 onto which the apparatus 710 are mounted. The apparatus 710 are beneficially designed so that half of them are operable to rotate in a first direction (for example in a clockwise rotational direction) and another half of them are operable to rotate in a second direction (for example in an anti-clockwise direction) so that the platform 720 experiences negligible overall turning torque in operation. The platform 720 is coupled to floats 740 for maintaining the platform 720 in an elevated position in respect of the ocean bed 270 but yet submerged within the ocean. One or more anchors 760 located on the ocean bed 270 are coupled via one or more corresponding flexible tethering lines 750 to the platform 720 for maintaining the platform 720 in position when tidal currents and/or ocean currents act upon the apparatus 710. Beneficially, the connecting arrangement 80 occurs from the one or more anchors 760. Alternatively, the connecting arrangement 80 is implemented from the platform 720. As an option, one or more of the apparatus 710 can be substituted with one or more of the apparatus 10 employing a single central mounting member 50.

The system 700 provides several potential advantages. Tidal currents and ocean currents tend to be stronger at an elevated distance from the ocean bed 270, thereby enabling more power to be generated by each apparatus 710 in comparison to it being mounted on the ocean bed 270, for example in a manner akin to FIG. 2. Moreover, when servicing is required, the one or more tethering lines 750 can be slackened and the platform 720 with its one or more apparatus 710 permitting to float up to the upper surface of the ocean. Once at the upper service of the ocean, personnel can readily access the one or more rotors 20 of the one or more apparatus 710 for servicing and maintenance purposes. Optionally, the one or more anchors 760 include winch equipment for enabling the tethering lines 750 to be selectively slackened or gathered in; such winch equipment can be controlled from above the upper surface of the ocean, for example from the vessel 600. Optionally, each apparatus 710 can be individually mounted on a corresponding foundation member 60 and used in a stand-alone manner akin to the apparatus 10 in FIG. 1 and FIG. 2.

Referring to FIG. 10, another energy production system pursuant to the present invention is indicated generally by 800 and includes a platform 810 onto which one or more apparatus indicated by 820 are each mounted via a plurality of equi-spaced sypporting members 830, for example four equi-spaced supporting members 830. Each apparatus 820 includes the aforementioned rotor 20 with its associated blades 30 mounted to its associated central bearing member 40. Optionally, the central bearing member 40 is implemented in a ring-like manner including a central open void 840, thereby assisting to reduce drag effects on associated blades 30. Use of four supporting members 830 enables torque developed at each apparatus 820 to be better resisted at the platform 810. Beneficially, the one or more apparatus 820 are operable to rotate in direct directions when subject to ocean currents or tidal currents, so that the platform 810 experiences a negligible overall torque when the system 800 is in operation.

Optionally, the platform 810 functions as an anchor and is mounted upon the ocean bed 270. Alternatively, the platform 810 is arranged to operate in a floating state, for example in a similar manner to the system 700 illustrated in FIG. 8. Optionally, the apparatus 820 can be individually mounted on a corresponding foundation member 60 as illustrated in an apparatus indicated by 900 in FIG. 11 , wherein four support equi-spaced support members 910 are employed.

The apparatus 10, 710, 820, 900 are capable of being employed in large numbers in energy farms, for example in a spatially-distributed matrix comprising thirty rows of such apparatus, wherein each row includes forty apparatus, namely a total of one thousand two hundred such apparatus. When each apparatus 10, 710, 820, 900 is operable to generate several

MegaWatts (MW) of power, such energy farms utilizing such a matrix of apparatus are each capable of generating a combined concurrent electrical output of approximately 1 GigaWatt (GW) resulting in many TeraWatt-hours (TWh) of electricity being produced annually.

It is estimated that the World presently consumes 80 million barrels of oil per day. Each barrel of oil corresponds to 1.7 MegaWatt-hours (MWh) energy. Such energy farms generating 1 GigaWatt (GW) of power are capable of providing energy equivalent to approximately 5000 barrels of oil per day. Extensive deployment of the energy farms in river estuaries and ocean regions, where a concentration of tidal flows and ocean currents occurs, is capable of generating electrical power corresponding to a significant portion of this World consumption. Moreover, such energy from the energy farms can be produced at a lower cost in comparison to energy generated from burning fossil fuels or from nuclear facilities. As such, the present invention is potentially capable of revolutionizing energy supply in the World in future when extensively deployed. Furthermore, the present invention is capable of being implemented using contemporary technologies without costly research in juxtaposition to an enormous research effort which is yet required for rendering nuclear fusion power practicable; whereas future nuclear fusion plants are likely to be highly complex installations, the present invention employs relatively simple technologies and is therefore a highly attractive technological proposition. Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims.

From the foregoing, it will be appreciated that the rotor 20 is beneficially implemented as a Darrieus-type rotor. However, the rotor 20 is susceptible to being implemented in other configurations within the scope of the present invention. For example, the rotor 20 is optionally implemented as a cycloturbine variant where the blades 30 of the rotor 20 are mounted so that they can be "pitched" with a result that they always present some angle of attack relative to a direction of incoming tidal current or ocean current. Such a cycloturbine is conveniently implemented with the blades 30 assuming a straight configuration in contradistinction to a helical configuration described in the foregoing. Moreover, such a cycloturbine is advantageous in that torque generated by such a cycloturbine rotor mounted in the apparatus 10, 710, 820 remains almost constant for a wide angle of incoming tidal currents or ocean currents. When straight blades 30 are employed for the rotor 20, for example three or four non-helical straight blades mounted to the rotor 20, the torque generated by the rotor 20 is relatively constant. Moreover, such a cycloturbine rotor 20 is self-starting, thereby avoiding for include the features 160. However, such a cycloturbine employs a blade pitching mechanism which is complex and generally heavy, and a stream direction sensor needs to be included for pitching the blades. However, a self-pitching configuration for the rotor 20 using polypropylene blades has been elucidated in the foregoing and provides a simple alternative solution for implementing the rotor 20.

Expressions such as "including", "comprising", "incorporating", "consisting of, "have", "is" used to describe and claim the present invention are intended to be construed in a non- exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.

Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.

Claims

1. An aquatic turbine apparatus (10, 710, 820), characterized in that the apparatus (10, 710, 820) includes:

a rotor (20) coupled to one or more sets of blades (30);

a bearing (170, 180, 190) for rotationally supporting the rotor (20) on a support arrangement (40); and

an energy pickup arrangement (100,110) disposed at least in part in the rotor (20) for generating energy when the rotor (20) rotates in operation relative to the support arrangement (40) in response to ocean currents and/or tidal currents acting upon the one or more sets of blades (30).

2. An aquatic turbine apparatus (10, 710, 820) as claimed in claim 1 , wherein the one or more sets of blades (30) are disposed in a form of a helical-blade rotor operable to extract energy from tidal currents and/or ocean currents irrespective of a direction of said currents.

3. An aquatic turbine apparatus (10, 710, 820) as claimed in claim 1 or 2, wherein the energy pickup arrangement (100, 110) is disposed spatially concurrently with the bearing (170, 180, 190).

4. An aquatic turbine apparatus (10, 710, 820) as claimed in claim 1 ,2 or 3, wherein the bearing (170, 180, 190) includes interface bearing surfaces defining one or more gaps (220) which are in fluid communication with an aquatic environment of the apparatus (10, 719, 820) when in operation.

5. An aquatic turbine apparatus (10, 710, 820) as claimed in claim 1 , 2, 3 or 4, wherein the bearing (170, 180, 190) is implemented in an interface between a glass surface (170) and a flexible polymeric surface (180, 190).

6. An aquatic turbine apparatus (10, 710, 820) as claimed in claim 5, wherein the flexible polymeric surface (180, 190) is implemented using a halogenated hydrocarbon polymer impregnated into a fabric carrier.

7. An aquatic turbine apparatus (10, 710, 820) as claimed in any one of the preceding claims, including one or more buoyancy tanks (90) for selectively filling with liquid or gas for raising or lowering the apparatus (10, 710, 820) within its aquatic environment during installation and/or maintenance.

8. An aquatic turbine apparatus (10, 710, 820) as claimed in any one of the preceding claims, including one or more vanes (160) exhibiting directional response to tidal currents and/or ocean currents received at the apparatus (10, 710, 820) for rendering the apparatus (10, 710, 820) self-starting in respect of turning of the rotor (20) relative to the support arrangement (40).

9. An aquatic turbine apparatus (10, 710, 820) as claimed in any one of the preceding claims, wherein the energy pickup arrangement (100, 110) is selectively operable to generate an initial starting torque to cause the rotor (20) to rotate from standstill relative to the support arrangement (40).

10. An aquatic turbine apparatus (10, 710, 820) as claimed in any one of the preceding claims, wherein the support arrangement (40) is mounted to a platform (60, 720, 810) via a mounting arrangement (50, 730, 830), said mounting arrangement (50, 730, 830) being implemented as at least one of:

(a) a single central supporting member (50);

(b) a pair of planar supporting members (730);

(c) four equi-spaced non-central supporting members (830).

11. An aquatic turbine apparatus (10, 710, 820) as claimed in any one of the preceding claims, wherein the energy pickup arrangement (100, 110) is encapsulated within the rotor (20) and the support arrangement (40) for isolating it from an aquatic environment of the apparatus (10, 710, 820) when in operation.

12. An aquatic turbine apparatus (10) as claimed in any of the preceding claims, including a connection gathering arrangement (260) for managing a connection (80) to said apparatus (10) when said apparatus (10) is raised and/or lowered within its aquatic environment during installation and/or maintenance.

13. An energy system (700, 800) including a plurality of apparatus (10, 710, 820) as claimed in any one of the preceding claims.

14. An energy system (700, 800) as claimed in claim 13, wherein the apparatus (10, 710, 810) include associated rotors (20) which are operable to rotate in mutually different directions for ensuring that said system (700, 800) experiences negligible overall torque when in operation.

15. An aquatic vessel (600) including a gripping and guiding arrangement (300, 660, 670, 680a, 680b) mounted thereto, said gripping and guiding arrangement being adapted to engage to one or more features (150) of the apparatus (10, 710, 820, 900) as claimed in any one of claims 1 to 12, for raising or lowering said apparatus (10, 710, 820, 900) whilst maintaining said apparatus (10, 710, 820, 900) in a constant angular orientation.

16. An aquatic vessel (600) as claimed in claim 15, wherein said gripping and guiding arrangement is operable to guide said apparatus within a plane of movement, said plane being substantially vertical and intersecting a longitudinal axis of a hull (610) of said vessel (600) for reducing a tendency for the vessel (600) to roll when said gripping and guiding arrangement is operable to raise or lower said apparatus.

17. A method of raising an apparatus as claimed in any one of claims 1 to 12, using an aquatic vessel (600) as claimed in any one of claims 15 to 16, said method including;

(a) engaging a gripping and guiding arrangement (300, 660, 670, 680a, 680b) mounted to said vessel (600) onto one or more features (150) of said apparatus (10);

(b) filling one or more buoyancy tanks (90, 695) of at least one of the gripping and guiding arrangement (300, 660, 670, 680a, 680b) and the apparatus (10) with a gas for increasing buoyancy to generate a buoyant lifting force on the apparatus (10); and

(c) guiding the apparatus (10) through its aquatic environment whilst said buoyant lifting force raises said apparatus (10) to an upper surface of its aquatic environment.

18. A method of lowering an apparatus as claimed in any one of claims 1 to 12, using an aquatic vessel (600) as claimed in any one of claims 15 to 16, said method including;

(b) filling one or more buoyancy tanks (90, 695) of at least one of the gripping and guiding arrangement (300, 660, 670, 680a, 680b) and the apparatus (10) with a liquid for decreasing buoyancy to generate a downward force on the apparatus (10); and

(c) guiding the apparatus (10) through its aquatic environment whilst said downward force lowers said apparatus (10) into its aquatic environment.

19. An aquatic turbine apparatus (10, 710, 820) including:

a rotor (20) coupled to one or more sets of blades (30),

an energy pickup arrangement (100,110) for generating energy when the rotor (20) rotates in operation relative to the support arrangement (40) in response to ocean currents and/or tidal currents acting upon the one or more sets of blades (30), wherein the bearing (170, 180, 190) is implemented in an interface between a glass surface (170) and a flexible polymeric surface (180, 190).

20. An aquatic turbine apparatus (10, 710, 820) as claimed in claim 19, wherein the bearing (170, 180, 190) includes interface bearing surfaces defining one or more gaps (220) which are in fluid communication with an aquatic environment of the apparatus (10, 719, 820) when in operation.

21. An aquatic bearing (170, 180, 190) for providing a rotational bearing interface between a first component (20) and a second component (40) for enabling the first component (20) to rotate relative to the second component (40) in operation, wherein the bearing (170, 180, 190) is implemented in an interface between a glass surface (170) and a flexible polymeric surface (180, 190) coupled to said components (20, 40).

22. An aquatic bearing (170, 180, 190) as claimed in claim 21 , wherein the bearing (170, 180, 190) includes interface bearing surfaces defining one or more gaps (220) which are in fluid communication with an aquatic environment of the bearing (170, 180, 190).