WO2008114019A2 - Deep water water current turbine installations - Google Patents

Deep water water current turbine installations Download PDF

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Publication number
WO2008114019A2
WO2008114019A2 PCT/GB2008/000985 GB2008000985W WO2008114019A2 WO 2008114019 A2 WO2008114019 A2 WO 2008114019A2 GB 2008000985 W GB2008000985 W GB 2008000985W WO 2008114019 A2 WO2008114019 A2 WO 2008114019A2
Authority
WO
WIPO (PCT)
Prior art keywords
support structure
water
turbine
mooring
buoyant
Prior art date
Application number
PCT/GB2008/000985
Other languages
French (fr)
Other versions
WO2008114019A3 (en
Inventor
Peter Leonard Fraenkel
Original Assignee
Marine Current Turbines Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Marine Current Turbines Limited filed Critical Marine Current Turbines Limited
Priority to EP08718822A priority Critical patent/EP2185809A2/en
Publication of WO2008114019A2 publication Critical patent/WO2008114019A2/en
Publication of WO2008114019A3 publication Critical patent/WO2008114019A3/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/26—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using tide energy
    • F03B13/264—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using tide energy using the horizontal flow of water resulting from tide movement
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B17/00—Other machines or engines
    • F03B17/06—Other machines or engines using liquid flow with predominantly kinetic energy conversion, e.g. of swinging-flap type, "run-of-river", "ultra-low head"
    • F03B17/061—Other machines or engines using liquid flow with predominantly kinetic energy conversion, e.g. of swinging-flap type, "run-of-river", "ultra-low head" with rotation axis substantially in flow direction
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B2017/0091—Offshore structures for wind turbines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2230/00—Manufacture
    • F05B2230/80—Repairing, retrofitting or upgrading methods
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/90—Mounting on supporting structures or systems
    • F05B2240/91—Mounting on supporting structures or systems on a stationary structure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/90—Mounting on supporting structures or systems
    • F05B2240/91—Mounting on supporting structures or systems on a stationary structure
    • F05B2240/915—Mounting on supporting structures or systems on a stationary structure which is vertically adjustable
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/90—Mounting on supporting structures or systems
    • F05B2240/93—Mounting on supporting structures or systems on a structure floating on a liquid surface
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/90—Mounting on supporting structures or systems
    • F05B2240/97—Mounting on supporting structures or systems on a submerged structure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This invention relates to turbines and to any other such devices capable of interacting with a flow of water in such a manner as to transfer or extract kinetic energy from the flow of water to a mechanically, pneumatically or hydraulically driven device.
  • This invention also relates more particularly to turbines or other such devices arranged to be driven by the action of a flow of water or other flowing medium.
  • the present invention relates in particular to the use of turbines and similar rotating devices capable of extracting kinetic energy from flowing water for the purposes of utilising such energy to produce either electricity, shaft power or pumping water or other liquids or gases for a required useful purpose.
  • said water driveable devices such as turbines driven by way of a relatively slowly rotating rotor are generally be connected mechanically, hydraulically or pneumatically) to a power train capable of absorbing the available energy from the relatively slow rotational speed of the device in response to relatively slow moving but forceful water movements, and converting the rotational movements into a more usable form such as electricity or pressurised fluid which may be readily transferred by way of cables or pipes (respectively) to a point of application to be usefully exploited.
  • Said power train may typically consist of a geared speed increaser means coupled to an electrical generator or to a hydraulic pump or in some cases the rotor may be directly coupled without recourse to a mechanical speed-increaser unit to a specially designed and matched slow-speed generator or pump.
  • a key aspect of the earlier aforementioned proposals is that they relate to devices which are mounted on a structure which needs to engage with the seabed sufficiently securely to resist the strong horizontal and torsional reactions resulting from the extraction of kinetic energy from the water flow.
  • the preferred solution to this problem was to provide a tubular monopile (or a multiplicity of such monopiles), set into a socket (or sockets) drilled into the seabed using known procedures, or alternatively set into a massive gravity foundation.
  • Such an arrangement produces a foundation with predictable characteristics and which can be designed to prevent any risk of movement relative to the seabed even under extreme dynamic loads.
  • a disadvantage of any structure of this kind that is intended to support water current turbines and which is engaged in some manner with the sea or riverbed, whether set into a socket or sockets or relying on its weight and friction to react the thrusts on the turbine or turbines, is that it becomes difficult to scale such a structure up in water with depths greater than 50 to 100 metres to raise the turbine or turbines to near the surface. This is because an excessively tall device, if mounted on the sea or river bed, will have a very large toppling or overturning moment that increases in proportion to the height of the mean thrust line above the sea or river bed. In short the structural complexity and cost become unacceptable beyond some height limit for "bottom- mounted" turbine rotors.
  • a further object of the present invention is the provision of a stable and robust support/foundation for one or more water current powered turbines or turbines capable of deployment in relatively deep fast moving water.
  • a preferred aspect of the invention provides a flowing water drivable turbine system, including a least one turbine assembly for converting the kinetic energy of passing water currents into usable energy, a support structure for mounting said at lest one turbine assembly, and means for maintaining the support structure a vertical/upright setting by the combined effects of associating the upper part of the support structure with provision of buoyancy means with means for the weight ways loading the lower part of the support structure.
  • the support structure is held in operational position by means of at least one cable, chain or other flexible tensile member attached to an anchor point on the seabed,.
  • said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or lengthening the free length of the cable member attached to an anchor point on the seabed, and wherein said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or lengthening the free length of the mooring cable, chain or other flexible member such that when shortened the structure is held in a near vertical position in the water column, and such that when the mooring is fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
  • the mooring cable or other tensile member is attached to a buoyant extension to the upper flotation vessel (or vessels) which supports the support structure in such manner that under the influence of the current flow in the water the buoyant extension will tend to counteract the moment caused by the thrust and drag upon the rotor or rotors of the turbine assembly or assemblies upon the support structure and the weight/loading in such manner as to at least assist in maintaining the support structure in said vertical/upright position.
  • buoyant extension to the upper floatation vessel may be separated from the upper floatation vessel (or vessels) by a structural member (or members) to position it further from the main structure and thereby increase the leverage to counteract the moments from turbine and structural drag,.
  • the aforementioned buoyant extension to the upper floatation vessel may be partially flooded or pumped out in order to vary its buoyancy to give the possibility for adjusting the restoring moment such that the structure carrying the turbines can be actively maintained close to a vertical
  • the support structure is of a buoyant construction.
  • the buoyancy means includes a buoyant support vessel or vessels.
  • the means for the weight ways ballesting/loading of the support structure includes a heavy ballasted/loaded vessel, vessels or other weighty component or components.
  • balasting/loading means is such that it may be rendered buoyant such that the structure undergoes flotation in such manner that it rotates/turns to a horizontal setting in the vicinity of the surface of the water as it rises to the surface of the water.
  • the support includes one or more column-like structural member(s) serving to support a plurality of turbine assemblies mounted on streamlined horizontal members set at intervals along the length of the structural member or members.
  • the means for loading/the support structure comprises a vessel which is such that it can be flooded to make it heavier than water when deploying the turbine assembly support structure or pumped empty of water (with air to replace it) so as to enable the structure to float and rise in a controllable manner to lie on the surface of the water, the arrangement being such as to enable the turbine assemblies be accessed for maintenance or repairs, or detached from its associated support structure for transport to shore.
  • the support structure is held in operational position by means of at least one cable, chain or other flexible tensile member attached to an anchor point on the seabed, and wherein said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or lengthening the free length of the mooring cable, chain or other flexible member such that when shortened the structure is held in a near vertical position in the water column, and such that when the mooring is fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
  • the support structure includes a plurality of laterally relatively spaced vertical column-like structural members and located between the floatation vessels near the top of the structure and the lowermost regions of the structure, and wherein said structural member are arranged to be used as additional means for balasting/loading the support structure
  • FIG. 1 is a front view of a first embodiment support arrangement for supporting a plurality of turbine installation whilst located in a column of water in such manner as to be driven by a flow of water;
  • Figure 2 is a side view of the arrangement of Figure 1;
  • Figure 3 schematically illustrates how the support arrangement and its associated turbines illustrated in Figures 1 and 2 may be floated to the surface by paying out mooring cable from the lower end;
  • Figure 4 is a front view of a second embodiment of a support arrangement for supporting a plurality of turbine installation whilst located in a column of water in such manner as to be driven by a flow of water;
  • Figure 5 is front view of a third embodiment of a support arrangement for supporting a single turbine installation in a column of water to be driven by a flow of water;
  • Figure 6 illustrates in side view a method to serving to overcome the tendency of the embodiment as illustrated in Figures 1 and 2 to take up an inclined position due to the thrust on the rotors and the drag of the structure;
  • Figure 7 illustrates a modification to the embodiment illustrated in Figure 6;
  • Figure 8 illustrates how the embodiments of Figures 6 and 7 may be caused to float horizontally
  • Figure 9 schematically illustrates an arrangement in which the mooring of the support structure member is tensioned by means of a winch;
  • Figure 10 illustrates the effect of the paying out of the mooring enables the support structure member to move to a horizontal position at water level;
  • Figure 11 schematically illustrates a modification of the arrangements provided for anchoring the the support structure member in a vertical position, with the figure indicating an initial position in which the member is floating at the water surface;
  • Figure 12 schematically illustrates the member when partially moved to an upright position
  • Figure 13 illustrates the support structure when engaged with its anchorage
  • FIG. 1 in which is illustrated a single vertical structural member 1 including a main body 2 mounting three horizontal or near horizontal cross arms/wings 3 mounted at intervals from the vertical structural member 1.
  • a turbine installation 4 is mounted to the outer end of each cross arm 3.
  • Each turbine installation includes a main body 5 including a power unit, that could include a gearbox and generator (not separately shown) and a rotor 6..
  • FIG. 1 shows a side elevation of the embodiment of Figure 1. From Figure 2 it can be noted that the heavy container 10 at the lowermost point of the floating structure has greater dimensions in the side elevation as compared with the front elevation in practice the dimensional relationship assists in minimising the heavy containers drag in the current flow, this flow being indicated by the arrow 14..
  • Figure 3 shows how the arrangement as illustrated in Figures 1 and 2 may be floated to the surface by paying out mooring cable 11 from the lower end of the member 1 and/or increasing the buoyancy of the lower tank 10 by pumping air into it to displace water from it.
  • Figure 4 shows that there can be more than one vertical support member 1 to allow a larger array of turbines installations 4 to be provided (12 in this example).
  • Two horizontal structural members 15 are shown as providing the means to give structural integrity to the array of turbines installations 4, but this is intended only as an example of how it may be done other means of providing the required structural integrity may be used.
  • Figure 5 schematically illustrates that the same basic structure illustrated in the Figure 1 can be used to support just a single turbine installation rotor, although in most cases a multiplicity of rotors will be preferred as being more cost-effective.
  • FIG. 6 shows a method serving to overcome the tendency of the embodiment as illustrated in Figures 1 and 2 to take up an inclined position due to the thrust on the rotors 6 and the drag of the buoyant support structure member 1 and the weight of the container 10.
  • the flotation tank 7 is provided with an extension 16 in the corm of a container to the floatation tank 7 .
  • This extension and its positioning will tend to impose a clockwise moment in the configuration as illustrated, due to the centre of buoyancy of the tank and extension combination being offset from the centre of gravity, while the current reacting with the rotors 6 and the structure member 1 will tend to cause an anticlockwise moment. If the turning moment from extension buoyant tank 16 is designed to be great enough to counteract the drag and thrust moment, then the structure member 1 will hang vertically when under load..
  • a refinement of the method of Figure 6 would be to make it possible to vary the buoyancy of the tank 16 by partially flooding it when the current velocity is low and pumping the water out to increase its buoyancy and hence the restoring moment, as the current velocity increases.
  • Figure 6 serves illustrate a basic principle of providing means to keep the turbine installation array close to vertical even when loaded by the water flow current.
  • the shape and detail design of key components of the turbine installation arrangements may be different.
  • the floatation tank 16 may be mounted on an extension member at a greater distance from tank 7 to increase its leverage and allow a smaller extension tank to be used.
  • Figure 7 shows how with the configuration illustrated in Figure 6, it may be practical to make the extension float 16 to which the mooring is fixed such that it can be detached from the main structure, acting then as a buoy to keep the mooring accessible.
  • FIG 8 illustrates a method of enabling the structure to move into a horizontal setting so as to bring the turbine installations above water level.
  • the lower tank 10 is filled with air so that the entire structure floats horizontally on the surface with the rotors and generators accessible to be maintained.
  • Figure 9 shows an alternative arrangement in which the mooring is tensioned from a winch 17 located preferably (but not necessarily) at sea level in the upper housing 7, such that the structure is held vertically in the water column by tensioning the mooring from the winch 17.
  • the mooring cable 11 is threaded through the length of the structure member 1 and emerges through guides 18 from the base of the tank 10.
  • a buoyant extension 16 is fitted to the upper floatation tank 7 such that as the moment caused by rotor thrust and structural drag tries to tilt the structure member 1 to the right (as viewed), the extra buoyancy of tank 16 counteracts this effect and thereby holds the structure member 1 near to the vertical position.
  • Figure 10 shows how the mooring cable may be paid out from the winch in the housing/tank 7 so that the lower part of the lower tank 10 may be allowed to float to the surface to allow maintenance of the turbines and/or removal and replacement of the entire system.
  • Figure 11, 12 and 13 show how the anchor weight as shown in Figures 1 to 10 can be replaced by a specially shaped foundation 20 into which the tank 10 is able to engage and nest.
  • the mooring 11 is attached to the foundation 20 as shown at the location t 21 .
  • the since this mooring is associated with the lower end of the support structure 1 the attachment of the mooring cable 10 to the foundation 20 followed by the winding-in of the mooring cable the lower end of the support structure 1 is caused to to sink towards the foundation 20 as a result of the winching in of the cable ( Figure 12) until the entire structure can be pulled into a socket 22 provided in the foundation 20 in the structure ( Figure 13) where it is held vertically against the forces of rotor thrust and drag.
  • the turbine structure has a hollow sleeve at its base which can fit over a spigot upstanding from the base structure.
  • the main innovative feature of this embodiment is provision for a turbine structure to be lowered down a cable to mate with a supporting foundation on the seabed. The process can of course be reversed by paying out cable the structure being buoyant will rise to the surface for maintenance or replacement.
  • buoyancy of the turbine structure is insufficient for it to float is that a barge or other vessel equipped with a crane would balance the submerged net weight of the structure during the procedure to install it or remove it from the foundation member.
  • the support structures associated with submergeable turbine assemblies can conveniently include can be an elongate buoyant structure which carries one or more turbine installations each including a turbine, associated rotor(s) and associated power train(s) (e, g. gearbox(es), electricity generator(s) or pump(s)), said, buoyant structure, being arranged for operational deployment so that it is able to float in a substantially vertically orientated sense, there being means located on and above the water surface for so supporting the buoyant structure that any turbine installation carried thereby will be so positioned that the turbine rotor or rotors thereof is/are operationally disposed with respect to a flow of water relative thereto.
  • a turbine associated rotor(s) and associated power train(s) (e, g. gearbox(es), electricity generator(s) or pump(s))
  • said, buoyant structure being arranged for operational deployment so that it is able to float in a substantially vertically orientated sense, there being means located on and above the water surface for so
  • the swept areas of the rotors are disposed in the same plane and normal to the direction of flow of the current.
  • the buoyant structure will be held in the required operational position by one (or more) mooring(s) attached to a suitable anchor (or anchors) or attachments) on the seabed or riverbed to counteract the thrust reaction from the rotors.
  • this invention proposes methods of and means for so suspending a water current driven turbine, or turbines in a water column in deep water in such position as to be able extract energy from the fastest moving currents in the water column.
  • An underlying aspect of the invention is the provision of means to position and deploy a turbine or an array of turbines in a suitably submerged position as to be able to extract energy effectively from passing currents and also to be able raise the aforementioned turbine or systems turbines to be able to access them from the surface, firstly to allow access for maintenance or repairs from above the surface of the sea or river and secondly to permit the entire system to be recovered to shore for major maintenance, repairs or component replacements.
  • a further aspect of the invention relates to the provision of means for installing one or more water current energy conversion rotors in the upper part of a fast moving and deep stream of water and for such means to be able to permit safe deployment and recovery of the turbine rotors and any power-trains using surface vessels with little or no underwater human intervention.
  • any kind of rotor or rotors may be used, including: axial flow (otherwise known as horizontal axis rotors or "propeller” type rotors) with an 'x' number of rotor blades; so called “Darrieus”, or cross-flow rotors or indeed any kind of rotor capable of converting kinetic energy from passing water currents into shaft power applicable for a useful purpose such as driving an electricity generator, a water pump or even an air compressor.
  • axial flow otherwise known as horizontal axis rotors or "propeller” type rotors
  • so called “Darrieus” or cross-flow rotors or indeed any kind of rotor capable of converting kinetic energy from passing water currents into shaft power applicable for a useful purpose such as driving an electricity generator, a water pump or even an air compressor.
  • it is immaterial to the concepts of the present invention as to whether each of the aforementioned rotor or rotors are open to the flow of water or are surrounded by a
  • the aforementioned mooring or moorings may be anchored/attached either to a massive gravity foundation of sufficient weight to hold the system securely in place through friction, or to anchors of other kinds such as ground anchors, piles driven into the seabed, etc.
  • the precise form of anchorage will be chosen in relation to the nature of the sea or river bed. In other words any suitable means of connecting the invention to an anchorage or anchorages on the sea or river bed may be used.
  • the mooring or moorings for the buoyant structure may comprise one or more flexible tensile members such as ropes, chains or cables, or it may comprise one or more rigid struts or ties connected to the buoyant structure and to the anchor or anchors via flexible joints, possibly of the ball and socket kind, or it may even comprise some combination of the aforementioned types of flexible and rigid members.
  • buoyant structure carrying the turbine installations and the associated rotors will have one or more vertical members of sufficient structural integrity to carry the required number of turbine installations.
  • the turbine installations will in most cases will be deployed in pairs on substantially horizontal streamlined support arms attached securely to the vertical member or members.
  • an array of turbine installations each having a relatively smaller rotor, said smaller turbine installations being so relatively positioned as to be able to sweep a predetermined cross section of the water current.
  • the proposal of the invention to make use of multiple rotors has the merit that they will rotate faster than a larger diameter rotor since the speed of rotation of a rotor is approximately inversely proportional to the rotor diameter, and this makes the transmission of shaft power from the rotor to an electricity generator or other device for applying the energy significantly less costly as mechanical transmission costs tend to be proportional to the input torque which tends to increase in proportion to the square of the rotor diameter.
  • a heavy mass is attached to the lowermost end of the substantially vertical column or columns that carry the rotors and forms the main support structure the arrangement being such that as to cause support structure column to tend to remain vertical or close to vertical.
  • said mass comprises one or more floodable tanks attached to the lower end of the vertical column (or columns).
  • ballast tank(s) These ballast tanks are so sized and of such a weight that when they are flooded the entire structure tends to hang vertically in the water column with the rotors entirely submerged but with the top of the structure breaking water surface in the form of the aforementioned buoyant displacement tank on and above the surface.
  • ballast tank or tanks
  • the lower end of the buoyant structure becomes sufficiently buoyant to rise to the surface whereby the entire structure turns through an angle of approximately 90 degrees such that the formerly vertical column or columns will lie on the surface substantially horizontal and supported by the air filled tanks at either end.
  • this embodiment may in fact be designed such that the mooring can be winched in such that the entire buoyant support structure floats substantially vertically but entirely submerged below the surface.
  • some appropriate form of remote control is provided to release and wind out the mooring in order to recover the system to the surface.
  • a feature of the offset support tanks is that if the lower part of the structure is made buoyant so as to raise it to the surface, either by pumping water out of a buoyancy tank or by paying out a taught mooring as described earlier, then the offset tank serves to raise the structure higher out of the water which serves to give better access to the turbine for maintenance and also makes the structure easier to tow or manoeuvre with tugs or other appropriate surface vessels.
  • a single point mooring may be attached to the top of the structure (at the surface) via a detachable buoy such that the centre of buoyancy is maintained upstream of the centre of gravity of the structure (to produce a moment which will counter the moment caused by thrust on the rotors and drag).
  • a further alternative is to use a mooring system connecting both the top and the bottom of the structure to an anchor point on the seabed so that the structure is held vertical (or approximately vertical) by the fixed lengths of the moorings; in such an arrangement the lower mooring line would generally be winched in to the lower part of the structure to position the structure vertically in the water column, and would be paid out in order to permit the structure to float such that it lies horizontally on the surface.
  • a further variation is an arrangement in which a buoyant structure is attached to an anchor point i.e., a heavy foundation seated on the seabed in such a way that a mooring cable, chain, or other flexible tensile member or a multiplicity of cables, chains or flexible members attached to the foundation can be winched into the base of the structure pulling the buoyant structure down against the floatation resulting from it being buoyant until the lower part of the buoyant structure actually engages with the foundation possibly being pulled into a socket in the foundation so that the foundation can assist in resisting the toppling moments that could be caused by thrust on the rotor or rotors and drag.
  • an anchor point i.e., a heavy foundation seated on the seabed in such a way that a mooring cable, chain, or other flexible tensile member or a multiplicity of cables, chains or flexible members attached to the foundation can be winched into the base of the structure pulling the buoyant structure down against the floatation resulting from it being buoyant until the lower part of the
  • the mooring cable or attachment member can form a conduit for the electrical power cable which can either be attached thereto, or threaded through it (if a hollow or tubular mooring is used
  • a further aspect of the invention relates to a flowing water driveable turbine system, wherein a turbine, or more generally a plurality of turbine assemblies (which may be of any viable type capable of converting the kinetic energy of the passing currents into usable power), is (or are) mounted for operational co-operation with a flow of water on a structure positioned in the water column in such a manner that the turbine(s) are deployed so as to sweep as large a cross-section of the current as possible while the structure is supported in a near vertical orientation by having a buoyant supporting vessel or vessels near its uppermost point and a heavy loaded/ ballasted vessel or vessels or other weighty component or components located near its lowermost point and moreover where the entire system can be caused to rotate from a near vertical orientation to a horizontal orientation on the surface of the sea for allowing access to the turbines and power trains from a surface vessel.
  • Another aspect of the invention provides an arrangement wherein the floating structure has one or more vertical column-like structural members which can support a plurality of turbines mounted on streamlined horizontal members set at intervals along the vertical length of the one or more column-like structural members.
  • the lowermost heavy loaded/ballasted vessel may be hollow, such that it can be flooded to make it heavier than water when deploying the turbine structure or it can be pumped empty of water (with air to replace it) so as to make it float such that the structure lies on the surface of the water can easily be accessed for maintenance or repairs, or can be detached from its mooring and towed to shore for major repairs or overhaul.
  • the structure is held in place by a single mooring consisting of a cable, chain or other flexible tensile member attached to an anchor point on the seabed, said mooring entering the lowermost part of the floating structure and being connected to a winch or other means for shortening or lengthening the free length of mooring such that when shortened the structure is held in a near vertical position in the water column, and when fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
  • a single mooring consisting of a cable, chain or other flexible tensile member attached to an anchor point on the seabed, said mooring entering the lowermost part of the floating structure and being connected to a winch or other means for shortening or lengthening the free length of mooring such that when shortened the structure is held in a near vertical position in the water column, and when fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
  • a plurality of vertical column-like structural members may be spaced laterally by suitable structural members set between the floatation vessels near the top of the structure and the ballasted heavy vessels near the lowermost point, moreover said structural members may be used to assist floatation at the top and to add to the weight at the bottom; i.e. may be used as extensions to the aforementioned floatation vessel(s) and heavy ballasted vessel(s)
  • the mooring cable or other tensile member is attached to a buoyant extension to the upper floatation vessel (or vessels) which supports the structure carrying turbine rotors in the water column such that under the influence of the current the buoyancy of the buoyant extension will tend to counteract the moment caused by the thrust and drag on the rotors and the structure and the weight of the mooring so as to better maintain the structure near to a vertical orientation in the water column.
  • buoyant extension to the upper floatation vessel (or vessels) may be separated from the upper floatation vessel (or vessels) by a structural member (or members) to position it further from the main structure and thereby increase the leverage to counteract the moments from turbine and structural drag,.
  • the aforementioned buoyant extension to the upper floatation vessel may be partially flooded or pumped out in order to vary its buoyancy to give the possibility for adjusting the restoring moment such that the structure carrying the turbines can be actively maintained close to a vertical orientation.
  • the aforementioned buoyant extension to the upper floatation vessel may be detachable from the upper floatation vessel so that it can float independently from the rest of the structure remaining attached to the mooring cable like a buoy, and the main structure carrying the turbine can then be removed and replaced for maintenance or repairs.
  • a floating structure is moored to a suitable anchor or anchors in a way that permits it to carry one or more water current kinetic energy conversion turbines such that they are close to being normal to the flow when the structure hangs vertically in the water column, but where through adjustment of the moorings or increasing the buoyancy of the lower part of the structure by pumping air into it to displace water (or both measures) the structure can rotate through approximately ninety degrees such that it lies flat on the surface to permit access for maintenance or to permit it to be detached and towed operational setting and also to enable the device to be recovered safely under what may be potentially difficult open-sea conditions.

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Abstract

A flowing water drivable turbine system, including a least one turbine assembly (4) for converting the kinetic energy of passing water currents into usable, energy, a support structure (1) for mounting said at least one turbine assembly, and means for maintaining the support structure a vertical /upright setting by the combined effects of associating the upper part of the support structure with provision of buoyancy means (7) with means (10) for weighting the lower part of the support structure which is held in operational position by means of at least one cable, chain or other flexible tensile member (11) attached to an anchor point (12) on the seabed (13).

Description

DEEP WATER WATER CURRENT TURBINE INSTALLATIONS
BACKGROUND OF THE INVENTION
This invention relates to turbines and to any other such devices capable of interacting with a flow of water in such a manner as to transfer or extract kinetic energy from the flow of water to a mechanically, pneumatically or hydraulically driven device.
This invention also relates more particularly to turbines or other such devices arranged to be driven by the action of a flow of water or other flowing medium.
Thus, the present invention relates in particular to the use of turbines and similar rotating devices capable of extracting kinetic energy from flowing water for the purposes of utilising such energy to produce either electricity, shaft power or pumping water or other liquids or gases for a required useful purpose.
It is known how to use turbines and rotating machinery for the purpose of extracting energy from moving water currents, for example in our British Patents GB 2311566 "Column Mounted Water Current Turbine", GB 2348250 'Pile Mounted Vertically Displaceable Water Turbine", and GB 2347976 "Variable Pitch Water Turbine". In these patents we have disclosed constructions pertaining to water driveable turbines where one or preferably two or more rotors may be arranged such that they are supported on a structure embedded in, or carried on a foundation set in the sea, river or estuary bed. We have also disclosed similar information in foreign patents derived from the above mentioned British patents, including among others, U509/914123, European EP 1183463, New Zealand N Z 514274 and Australian AU 766741, all entitled "Water Current Turbine Sleeve Mounting". There are also known examples of such prior art from other sources. It should be noted that said water driveable devices such as turbines driven by way of a relatively slowly rotating rotor are generally be connected mechanically, hydraulically or pneumatically) to a power train capable of absorbing the available energy from the relatively slow rotational speed of the device in response to relatively slow moving but forceful water movements, and converting the rotational movements into a more usable form such as electricity or pressurised fluid which may be readily transferred by way of cables or pipes (respectively) to a point of application to be usefully exploited. Said power train may typically consist of a geared speed increaser means coupled to an electrical generator or to a hydraulic pump or in some cases the rotor may be directly coupled without recourse to a mechanical speed-increaser unit to a specially designed and matched slow-speed generator or pump.
A key aspect of the earlier aforementioned proposals is that they relate to devices which are mounted on a structure which needs to engage with the seabed sufficiently securely to resist the strong horizontal and torsional reactions resulting from the extraction of kinetic energy from the water flow. Moreover, in the aforementioned embodiments of our water current turbine inventions as disclosed in the specifications above mentioned the preferred solution to this problem was to provide a tubular monopile (or a multiplicity of such monopiles), set into a socket (or sockets) drilled into the seabed using known procedures, or alternatively set into a massive gravity foundation. Such an arrangement produces a foundation with predictable characteristics and which can be designed to prevent any risk of movement relative to the seabed even under extreme dynamic loads.
A disadvantage of any structure of this kind that is intended to support water current turbines and which is engaged in some manner with the sea or riverbed, whether set into a socket or sockets or relying on its weight and friction to react the thrusts on the turbine or turbines, is that it becomes difficult to scale such a structure up in water with depths greater than 50 to 100 metres to raise the turbine or turbines to near the surface. This is because an excessively tall device, if mounted on the sea or river bed, will have a very large toppling or overturning moment that increases in proportion to the height of the mean thrust line above the sea or river bed. In short the structural complexity and cost become unacceptable beyond some height limit for "bottom- mounted" turbine rotors.
An important reason for seeking to position any turbine rotor (or rotors) as near to the surface as possible is that, in general, it is well known that flowing water currents are fastest near the surface and almost stationary where they flow over the sea bed. As a result, typically some 75% of the energy in a flowing water current tends to be in the upper 50% of the water column with a typical velocity shear distribution. Hence a turbine rotor or rotors located low in the water column will be bypassed by most of the energy of the current passing over the top of it (or them).
OBJECTS OF THE INVENTION
It is an object of the invention to provide a turbine installation that is capable of avoiding or at least significantly reducing the problems arising from the utilisation of turbine installations in deep water conditions.
A further object of the present invention is the provision of a stable and robust support/foundation for one or more water current powered turbines or turbines capable of deployment in relatively deep fast moving water..
STATEMENTS OF THE INVENTION
Broadly according to a first aspect of the invention there is provided a method of operationally locating at least one turbine installation in a vertical column of deep water at such position that the turbine of the installation is operationally located at a region of the fastest range of water flow in the column of deep water
A preferred aspect of the invention provides a flowing water drivable turbine system, including a least one turbine assembly for converting the kinetic energy of passing water currents into usable energy, a support structure for mounting said at lest one turbine assembly, and means for maintaining the support structure a vertical/upright setting by the combined effects of associating the upper part of the support structure with provision of buoyancy means with means for the weight ways loading the lower part of the support structure..
Preferably the support structure is held in operational position by means of at least one cable, chain or other flexible tensile member attached to an anchor point on the seabed,.
Conveniently, said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or lengthening the free length of the cable member attached to an anchor point on the seabed, and wherein said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or lengthening the free length of the mooring cable, chain or other flexible member such that when shortened the structure is held in a near vertical position in the water column, and such that when the mooring is fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
hi a preferred arrangement the mooring cable or other tensile member is attached to a buoyant extension to the upper flotation vessel (or vessels) which supports the support structure in such manner that under the influence of the current flow in the water the buoyant extension will tend to counteract the moment caused by the thrust and drag upon the rotor or rotors of the turbine assembly or assemblies upon the support structure and the weight/loading in such manner as to at least assist in maintaining the support structure in said vertical/upright position.
Conveniently, where the buoyant extension to the upper floatation vessel (or vessels) may be separated from the upper floatation vessel (or vessels) by a structural member (or members) to position it further from the main structure and thereby increase the leverage to counteract the moments from turbine and structural drag,.
In a preferred arrangement the aforementioned buoyant extension to the upper floatation vessel may be partially flooded or pumped out in order to vary its buoyancy to give the possibility for adjusting the restoring moment such that the structure carrying the turbines can be actively maintained close to a vertical
In particular the support structure is of a buoyant construction.
In a preferred construction the buoyancy means includes a buoyant support vessel or vessels.
In particular, the means for the weight ways ballesting/loading of the support structure includes a heavy ballasted/loaded vessel, vessels or other weighty component or components.
Also the balasting/loading means is such that it may be rendered buoyant such that the structure undergoes flotation in such manner that it rotates/turns to a horizontal setting in the vicinity of the surface of the water as it rises to the surface of the water.
In practice, the support includes one or more column-like structural member(s) serving to support a plurality of turbine assemblies mounted on streamlined horizontal members set at intervals along the length of the structural member or members.
In a particular construction the means for loading/the support structure comprises a vessel which is such that it can be flooded to make it heavier than water when deploying the turbine assembly support structure or pumped empty of water (with air to replace it) so as to enable the structure to float and rise in a controllable manner to lie on the surface of the water, the arrangement being such as to enable the turbine assemblies be accessed for maintenance or repairs, or detached from its associated support structure for transport to shore..
Preferably, the support structure is held in operational position by means of at least one cable, chain or other flexible tensile member attached to an anchor point on the seabed, and wherein said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or lengthening the free length of the mooring cable, chain or other flexible member such that when shortened the structure is held in a near vertical position in the water column, and such that when the mooring is fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
In a further construction the support structure includes a plurality of laterally relatively spaced vertical column-like structural members and located between the floatation vessels near the top of the structure and the lowermost regions of the structure, and wherein said structural member are arranged to be used as additional means for balasting/loading the support structure
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention and to show how to carry the same into effect reference will now be made to the accompanying drawings in which: - Figure 1 is a front view of a first embodiment support arrangement for supporting a plurality of turbine installation whilst located in a column of water in such manner as to be driven by a flow of water;
Figure 2 is a side view of the arrangement of Figure 1;
Figure 3 schematically illustrates how the support arrangement and its associated turbines illustrated in Figures 1 and 2 may be floated to the surface by paying out mooring cable from the lower end;
Figure 4 is a front view of a second embodiment of a support arrangement for supporting a plurality of turbine installation whilst located in a column of water in such manner as to be driven by a flow of water;
Figure 5 is front view of a third embodiment of a support arrangement for supporting a single turbine installation in a column of water to be driven by a flow of water;
Figure 6 illustrates in side view a method to serving to overcome the tendency of the embodiment as illustrated in Figures 1 and 2 to take up an inclined position due to the thrust on the rotors and the drag of the structure;
Figure 7 illustrates a modification to the embodiment illustrated in Figure 6;
Figure 8 illustrates how the embodiments of Figures 6 and 7 may be caused to float horizontally;
Figure 9 schematically illustrates an arrangement in which the mooring of the support structure member is tensioned by means of a winch; Figure 10 illustrates the effect of the paying out of the mooring enables the support structure member to move to a horizontal position at water level;
Figure 11 schematically illustrates a modification of the arrangements provided for anchoring the the support structure member in a vertical position, with the figure indicating an initial position in which the member is floating at the water surface;
Figure 12 schematically illustrates the member when partially moved to an upright position, and
Figure 13 illustrates the support structure when engaged with its anchorage
Referring now to Figures 1 and 2 in which is illustrated a single vertical structural member 1 including a main body 2 mounting three horizontal or near horizontal cross arms/wings 3 mounted at intervals from the vertical structural member 1.. A turbine installation 4 is mounted to the outer end of each cross arm 3. . Each turbine installation includes a main body 5 including a power unit, that could include a gearbox and generator (not separately shown) and a rotor 6..
The structural member 1 the cross arms 3 , and the turbine installations 4 are supported by a large buoyant float 7 which is located at the water surface 8. It will thus be noted that in the arrangement of Figure 1 there are six turbine installations carried by the support member 1. In practice this number can be varied according to requirements.
The lower end 9 of the vertical structural member 1 is held down by a combination of the weight of a container 10 (which may if necessary be flooded) and/or the tension in a mooring 11 attached to a massive anchor weight 12 located on the sea or river bed 13.. Figure 2 shows a side elevation of the embodiment of Figure 1. From Figure 2 it can be noted that the heavy container 10 at the lowermost point of the floating structure has greater dimensions in the side elevation as compared with the front elevation in practice the dimensional relationship assists in minimising the heavy containers drag in the current flow, this flow being indicated by the arrow 14..
Figure 3 shows how the arrangement as illustrated in Figures 1 and 2 may be floated to the surface by paying out mooring cable 11 from the lower end of the member 1 and/or increasing the buoyancy of the lower tank 10 by pumping air into it to displace water from it.
Figure 4 shows that there can be more than one vertical support member 1 to allow a larger array of turbines installations 4 to be provided (12 in this example). Two horizontal structural members 15 are shown as providing the means to give structural integrity to the array of turbines installations 4, but this is intended only as an example of how it may be done other means of providing the required structural integrity may be used.
Figure 5 schematically illustrates that the same basic structure illustrated in the Figure 1 can be used to support just a single turbine installation rotor, although in most cases a multiplicity of rotors will be preferred as being more cost-effective.
Figure 6 shows a method serving to overcome the tendency of the embodiment as illustrated in Figures 1 and 2 to take up an inclined position due to the thrust on the rotors 6 and the drag of the buoyant support structure member 1 and the weight of the container 10.. In the arrangement shown in Figure 6 the flotation tank 7 is provided with an extension 16 in the corm of a container to the floatation tank 7 . This extension and its positioning will tend to impose a clockwise moment in the configuration as illustrated, due to the centre of buoyancy of the tank and extension combination being offset from the centre of gravity, while the current reacting with the rotors 6 and the structure member 1 will tend to cause an anticlockwise moment. If the turning moment from extension buoyant tank 16 is designed to be great enough to counteract the drag and thrust moment, then the structure member 1 will hang vertically when under load..
A refinement of the method of Figure 6 would be to make it possible to vary the buoyancy of the tank 16 by partially flooding it when the current velocity is low and pumping the water out to increase its buoyancy and hence the restoring moment, as the current velocity increases.
It will be noted that Figure 6 serves illustrate a basic principle of providing means to keep the turbine installation array close to vertical even when loaded by the water flow current. In practice the shape and detail design of key components of the turbine installation arrangements may be different. For example the floatation tank 16 may be mounted on an extension member at a greater distance from tank 7 to increase its leverage and allow a smaller extension tank to be used.
Figure 7 shows how with the configuration illustrated in Figure 6, it may be practical to make the extension float 16 to which the mooring is fixed such that it can be detached from the main structure, acting then as a buoy to keep the mooring accessible.
Referring now to Figure 8, which illustrates a method of enabling the structure to move into a horizontal setting so as to bring the turbine installations above water level. In this method the lower tank 10 is filled with air so that the entire structure floats horizontally on the surface with the rotors and generators accessible to be maintained.
It should be noted that whilst the support structure is in the floating position shown in Figure 8 it can be towed to shore for repairs or replacement. Figure 9 shows an alternative arrangement in which the mooring is tensioned from a winch 17 located preferably (but not necessarily) at sea level in the upper housing 7, such that the structure is held vertically in the water column by tensioning the mooring from the winch 17. In this arrangement the mooring cable 11 is threaded through the length of the structure member 1 and emerges through guides 18 from the base of the tank 10. hi this case a buoyant extension 16 is fitted to the upper floatation tank 7 such that as the moment caused by rotor thrust and structural drag tries to tilt the structure member 1 to the right (as viewed), the extra buoyancy of tank 16 counteracts this effect and thereby holds the structure member 1 near to the vertical position.
Figure 10 shows how the mooring cable may be paid out from the winch in the housing/tank 7 so that the lower part of the lower tank 10 may be allowed to float to the surface to allow maintenance of the turbines and/or removal and replacement of the entire system.
Figure 11, 12 and 13 show how the anchor weight as shown in Figures 1 to 10 can be replaced by a specially shaped foundation 20 into which the tank 10 is able to engage and nest. The mooring 11 is attached to the foundation 20 as shown at the location t 21 . The since this mooring is associated with the lower end of the support structure 1 the attachment of the mooring cable 10 to the foundation 20 followed by the winding-in of the mooring cable the lower end of the support structure 1 is caused to to sink towards the foundation 20 as a result of the winching in of the cable (Figure 12) until the entire structure can be pulled into a socket 22 provided in the foundation 20 in the structure (Figure 13) where it is held vertically against the forces of rotor thrust and drag.
An alternative embodiment not illustrated would be that the turbine structure has a hollow sleeve at its base which can fit over a spigot upstanding from the base structure. The main innovative feature of this embodiment is provision for a turbine structure to be lowered down a cable to mate with a supporting foundation on the seabed. The process can of course be reversed by paying out cable the structure being buoyant will rise to the surface for maintenance or replacement.
It the case where the buoyancy of the turbine structure is insufficient for it to float is that a barge or other vessel equipped with a crane would balance the submerged net weight of the structure during the procedure to install it or remove it from the foundation member.
From the above it will be apparent that the support structures associated with submergeable turbine assemblies can conveniently include can be an elongate buoyant structure which carries one or more turbine installations each including a turbine, associated rotor(s) and associated power train(s) (e, g. gearbox(es), electricity generator(s) or pump(s)), said, buoyant structure, being arranged for operational deployment so that it is able to float in a substantially vertically orientated sense, there being means located on and above the water surface for so supporting the buoyant structure that any turbine installation carried thereby will be so positioned that the turbine rotor or rotors thereof is/are operationally disposed with respect to a flow of water relative thereto.
Conveniently in the case of an axial flow turbine the rotor or rotors thereof will require the plane of rotation of the associated rotor to be approximately normal to the flow of water .
Preferably in practice when several turbine installations are involved they will be arranged such that when in their operational positions the rotor(s) of any such installation does not at any time intercept the wakes from any neighbouring rotors,
In a preferred arrangement the swept areas of the rotors are disposed in the same plane and normal to the direction of flow of the current. Preferably when several assemblies are involved the buoyant structure will be held in the required operational position by one (or more) mooring(s) attached to a suitable anchor (or anchors) or attachments) on the seabed or riverbed to counteract the thrust reaction from the rotors.
Therefore, this invention proposes methods of and means for so suspending a water current driven turbine, or turbines in a water column in deep water in such position as to be able extract energy from the fastest moving currents in the water column..
Furthermore, since in practice another vital requirement with any submarine device is to provide means both to enable the deployment of the device to its operational setting and also to enable the device to be recovered safely under what may be potentially difficult open-sea conditions.
An underlying aspect of the invention is the provision of means to position and deploy a turbine or an array of turbines in a suitably submerged position as to be able to extract energy effectively from passing currents and also to be able raise the aforementioned turbine or systems turbines to be able to access them from the surface, firstly to allow access for maintenance or repairs from above the surface of the sea or river and secondly to permit the entire system to be recovered to shore for major maintenance, repairs or component replacements.
Thus a further aspect of the invention relates to the provision of means for installing one or more water current energy conversion rotors in the upper part of a fast moving and deep stream of water and for such means to be able to permit safe deployment and recovery of the turbine rotors and any power-trains using surface vessels with little or no underwater human intervention.
It should be noted that in so far as the present invention is concerned that any kind of rotor or rotors may be used, including: axial flow (otherwise known as horizontal axis rotors or "propeller" type rotors) with an 'x' number of rotor blades; so called "Darrieus", or cross-flow rotors or indeed any kind of rotor capable of converting kinetic energy from passing water currents into shaft power applicable for a useful purpose such as driving an electricity generator, a water pump or even an air compressor. Moreover, it is immaterial to the concepts of the present invention as to whether each of the aforementioned rotor or rotors are open to the flow of water or are surrounded by a duct or venturi.
In practice, the aforementioned mooring or moorings may be anchored/attached either to a massive gravity foundation of sufficient weight to hold the system securely in place through friction, or to anchors of other kinds such as ground anchors, piles driven into the seabed, etc. The precise form of anchorage will be chosen in relation to the nature of the sea or river bed. In other words any suitable means of connecting the invention to an anchorage or anchorages on the sea or river bed may be used.
Conveniently the mooring or moorings for the buoyant structure may comprise one or more flexible tensile members such as ropes, chains or cables, or it may comprise one or more rigid struts or ties connected to the buoyant structure and to the anchor or anchors via flexible joints, possibly of the ball and socket kind, or it may even comprise some combination of the aforementioned types of flexible and rigid members.
Preferably the buoyant structure carrying the turbine installations and the associated rotors will have one or more vertical members of sufficient structural integrity to carry the required number of turbine installations.
Preferably also the turbine installations will in most cases will be deployed in pairs on substantially horizontal streamlined support arms attached securely to the vertical member or members. In accordance with a further aspect of the invention as an alternative to the utilisation of a single turbine installation having a relatively large diameter rotor there is provided an array of turbine installations each having a relatively smaller rotor, said smaller turbine installations being so relatively positioned as to be able to sweep a predetermined cross section of the water current.
In practice, the proposal of the invention to make use of multiple rotors has the merit that they will rotate faster than a larger diameter rotor since the speed of rotation of a rotor is approximately inversely proportional to the rotor diameter, and this makes the transmission of shaft power from the rotor to an electricity generator or other device for applying the energy significantly less costly as mechanical transmission costs tend to be proportional to the input torque which tends to increase in proportion to the square of the rotor diameter.
Conveniently a heavy mass is attached to the lowermost end of the substantially vertical column or columns that carry the rotors and forms the main support structure the arrangement being such that as to cause support structure column to tend to remain vertical or close to vertical.
Preferably said mass comprises one or more floodable tanks attached to the lower end of the vertical column (or columns).
These tanks will hereinafter be referred to as "ballast tank(s)". These ballast tanks are so sized and of such a weight that when they are flooded the entire structure tends to hang vertically in the water column with the rotors entirely submerged but with the top of the structure breaking water surface in the form of the aforementioned buoyant displacement tank on and above the surface.
However in accordance with the concepts of the invention when the ballast tank (or tanks) is (are) pumped full of air (using suitable on board pumping or air compressing equipment), then the lower end of the buoyant structure becomes sufficiently buoyant to rise to the surface whereby the entire structure turns through an angle of approximately 90 degrees such that the formerly vertical column or columns will lie on the surface substantially horizontal and supported by the air filled tanks at either end.
It will be appreciated that in order to permit this to happen the mooring or moorings in some cases will need to be disconnected or extended by paying out extra cable, chain or other form of flexible connection.
When a single point flexible mooring is involved it is proposed as an alternative to using a heavy mass possibly in the form of a ballast tank to use means for winching or reeling in the mooring to pull the lower end of the structure down into the water column. With this arrangement it is arranged that anchorage will have sufficient weight or attachment integrity to the seabed or river bed to permit the tension in the mooring to exceed the buoyancy forces seeking to keep the buoyant structure floating horizontally on the surface.
This proposal provides an embodiment of the support structure that can be regarded as forming tension-leg buoy with one or more turbine installations and associated rotors attached thereto
In practice .this embodiment may in fact be designed such that the mooring can be winched in such that the entire buoyant support structure floats substantially vertically but entirely submerged below the surface. In this case some appropriate form of remote control is provided to release and wind out the mooring in order to recover the system to the surface.
In order to counteract a possible problem arising when the buoyant support structure hangs vertically at slack tide, or when not exposed to a significant current, in that it will tend to take up an increasing angle of inclination when the current increases as a result of the moment developed by the thrust forces on the turbine rotors (or rotor) and the drag of the structure reacting to the mooring forces and that the. thrust of the rotors will tend to deflect the floating support structure into an inclined position, in the direction of the flow of the current, it is proposed to offset the buoyant floatation tank which emerges from the surface in such a way that the centre of buoyancy is upstream of the main vertical support column or columns and will generate a moment tending to incline the column in the opposite direction to that of the moments caused by the thrust on the turbine rotors, the mooring reaction and the gravity forces.
With this arrangement by providing suitably shaped buoyancy tanks at the surface the vertical orientation of the main rotor support column or columns can be substantially maintained (although some small variation in verticality my occur). Small offsets from vertical orientation will not significantly reduce the efficiency of the turbines as for example an axial flow rotor will in effect have its output reduced by a factor of cosine X, where X is the angle the rotor makes to the current. So long as this is no more than 10 degrees from normal to the current, cosine X will be < 2%. In other words even with a misalignment of 10 degrees the efficiency will remain at over 98% of what could be expected with no misalignment.
A feature of the offset support tanks is that if the lower part of the structure is made buoyant so as to raise it to the surface, either by pumping water out of a buoyancy tank or by paying out a taught mooring as described earlier, then the offset tank serves to raise the structure higher out of the water which serves to give better access to the turbine for maintenance and also makes the structure easier to tow or manoeuvre with tugs or other appropriate surface vessels.
Alternative methods to moor and to maintain the stability and correct orientation of the floating structure can also be applied; for example a single point mooring may be attached to the top of the structure (at the surface) via a detachable buoy such that the centre of buoyancy is maintained upstream of the centre of gravity of the structure (to produce a moment which will counter the moment caused by thrust on the rotors and drag). A further alternative is to use a mooring system connecting both the top and the bottom of the structure to an anchor point on the seabed so that the structure is held vertical (or approximately vertical) by the fixed lengths of the moorings; in such an arrangement the lower mooring line would generally be winched in to the lower part of the structure to position the structure vertically in the water column, and would be paid out in order to permit the structure to float such that it lies horizontally on the surface.
A further variation is an arrangement in which a buoyant structure is attached to an anchor point i.e., a heavy foundation seated on the seabed in such a way that a mooring cable, chain, or other flexible tensile member or a multiplicity of cables, chains or flexible members attached to the foundation can be winched into the base of the structure pulling the buoyant structure down against the floatation resulting from it being buoyant until the lower part of the buoyant structure actually engages with the foundation possibly being pulled into a socket in the foundation so that the foundation can assist in resisting the toppling moments that could be caused by thrust on the rotor or rotors and drag. With this arrangement when maintenance is required the engagement with the foundation may be broken by paying out the mooring and letting the structure float to the surface.
In all cases mentioned the mooring cable or attachment member can form a conduit for the electrical power cable which can either be attached thereto, or threaded through it (if a hollow or tubular mooring is used
A further aspect of the invention relates to a flowing water driveable turbine system, wherein a turbine, or more generally a plurality of turbine assemblies (which may be of any viable type capable of converting the kinetic energy of the passing currents into usable power), is (or are) mounted for operational co-operation with a flow of water on a structure positioned in the water column in such a manner that the turbine(s) are deployed so as to sweep as large a cross-section of the current as possible while the structure is supported in a near vertical orientation by having a buoyant supporting vessel or vessels near its uppermost point and a heavy loaded/ ballasted vessel or vessels or other weighty component or components located near its lowermost point and moreover where the entire system can be caused to rotate from a near vertical orientation to a horizontal orientation on the surface of the sea for allowing access to the turbines and power trains from a surface vessel.
Another aspect of the invention provides an arrangement wherein the floating structure has one or more vertical column-like structural members which can support a plurality of turbines mounted on streamlined horizontal members set at intervals along the vertical length of the one or more column-like structural members.
In a preferred arrangement where the lowermost heavy loaded/ballasted vessel may be hollow, such that it can be flooded to make it heavier than water when deploying the turbine structure or it can be pumped empty of water (with air to replace it) so as to make it float such that the structure lies on the surface of the water can easily be accessed for maintenance or repairs, or can be detached from its mooring and towed to shore for major repairs or overhaul.
Conveniently the structure is held in place by a single mooring consisting of a cable, chain or other flexible tensile member attached to an anchor point on the seabed, said mooring entering the lowermost part of the floating structure and being connected to a winch or other means for shortening or lengthening the free length of mooring such that when shortened the structure is held in a near vertical position in the water column, and when fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
Conveniently a plurality of vertical column-like structural members may be spaced laterally by suitable structural members set between the floatation vessels near the top of the structure and the ballasted heavy vessels near the lowermost point, moreover said structural members may be used to assist floatation at the top and to add to the weight at the bottom; i.e. may be used as extensions to the aforementioned floatation vessel(s) and heavy ballasted vessel(s)
Conveniently the mooring cable or other tensile member is attached to a buoyant extension to the upper floatation vessel (or vessels) which supports the structure carrying turbine rotors in the water column such that under the influence of the current the buoyancy of the buoyant extension will tend to counteract the moment caused by the thrust and drag on the rotors and the structure and the weight of the mooring so as to better maintain the structure near to a vertical orientation in the water column.
Where the buoyant extension to the upper floatation vessel (or vessels) may be separated from the upper floatation vessel (or vessels) by a structural member (or members) to position it further from the main structure and thereby increase the leverage to counteract the moments from turbine and structural drag,.
Preferably the aforementioned buoyant extension to the upper floatation vessel may be partially flooded or pumped out in order to vary its buoyancy to give the possibility for adjusting the restoring moment such that the structure carrying the turbines can be actively maintained close to a vertical orientation.
Conveniently the aforementioned buoyant extension to the upper floatation vessel may be detachable from the upper floatation vessel so that it can float independently from the rest of the structure remaining attached to the mooring cable like a buoy, and the main structure carrying the turbine can then be removed and replaced for maintenance or repairs.
Essentially an arrangement where a floating structure is moored to a suitable anchor or anchors in a way that permits it to carry one or more water current kinetic energy conversion turbines such that they are close to being normal to the flow when the structure hangs vertically in the water column, but where through adjustment of the moorings or increasing the buoyancy of the lower part of the structure by pumping air into it to displace water (or both measures) the structure can rotate through approximately ninety degrees such that it lies flat on the surface to permit access for maintenance or to permit it to be detached and towed operational setting and also to enable the device to be recovered safely under what may be potentially difficult open-sea conditions.

Claims

1 A flowing water drivable turbine system, including a least one turbine assembly for converting the kinetic energy of passing water currents into usable energy, a support structure for mounting said at lest one turbine assembly, and means for maintaining the support structure a vertical/upright setting by the combined effects of associating the upper part of the support structure with provision of buoyancy means with means for the weight ways loading the lower part of the support structure..
2 A system as claimed in claim 1, wherein the support structure is held in operational position by means of at least one cable, chain or other flexible tensile member attached to an anchor point on the seabed,.
3. A system as claimed in claim 2, and wherein said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or lengthening the free length of the cable member attached to an anchor point on the seabed, and wherein said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or lengthening the free length of the mooring cable, chain or other flexible member such that when shortened the structure is held in a near vertical position in the water column, and such that when the mooring is fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
4. A system as claimed in claim 3, and wherein the mooring cable or other tensile member is attached to a buoyant extension to the upper flotation vessel (or vessels) which supports the support structure in such manner that under the influence of the current flow in the water the buoyant extension will tend to counteract the moment caused by the thrust and drag upon the rotor or rotors of the turbine assembly or assemblies upon the support structure and the weight/loading in such manner as to at least assist in maintaining the support structure in said verical/upright position.
5. An arrangement as in Claim 4 where the buoyant extension to the upper floatation vessel (or vessels) may be separated from the upper floatation vessel (or vessels) by a structural member (or members) to position it further from the main structure and thereby increase the leverage to counteract the moments from turbine and structural drag,.
6. An arrangement as in Claims 5 and 6. wherein the aforementioned buoyant extension to the upper floatation vessel may be partially flooded or pumped out in order to vary its buoyancy to give the possibility for adjusting the restoring moment such that the structure carrying the turbines can be actively maintained close to a vertical
7. A flowing water drivable turbine system as claimed in any one of claims 1 to 6, and wherein the support structure is of a buoyant construction.
8. A flowing water drivable turbine system as claimed in claim any one of claims 1 to 7, and wherein the buoyancy means includes a buoyant support vessel or vessels.
9. A flowing water drivable turbine assembly as claimed in claim any one of claims 1 to 8, and wherein the means for the weight ways ballesting/loading of the support structure includes a heavy ballasted/loaded vessel, vessels or other weighty component or components.
10. A turbine system as claimed in any one of claims 1 to 9, and wherein the balasting/loading means is such that it may be rendered buoyant such that the structure undergoes flotation in such manner that it rotates/turns to a horizontal setting in the vicinity of the surface of the water as it rises to the surface of the water.
11.. A system as claimed in any one of claims 1 to 10, and wherein the support includes one or more column-like structural member(s) serving to support a plurality of turbine assemblies mounted on streamlined horizontal members set at intervals along the length of the structural member or members.
12. A system as claimed in any one of claims 1 to 11, and wherein the means for loading/the support structure comprises a vessel which is such that it can be flooded to make it heavier than water when deploying the turbine assembly 0 support structure or pumped empty of water (with air to replace it) so as to enable the structure to float and rise in a controllable manner to lie on the surface of the water, the arrangement being such as to enable the turbine assemblies be accessed for maintenance or repairs, or detached from its associated support structure for transport to shore..
15 13. . A system as claimed any one of claims 1 to 11, wherein the support structure is held in operational position by means of at least one cable, chain or other flexible tensile member attached to an anchor point on the seabed, and wherein said mooring is arranged to enter the lowermost part of the support structure and to be connected to a winch or other means for shortening or
20 lengthening the free length of the mooring cable, chain or other flexible member such that when shortened the structure is held in a near vertical position in the water column, and such that when the mooring is fully paid out the structure may turn through ninety degrees and float horizontally on the surface.
14. A system as claimed in any one of claims 1 to 13, wherein the support 25 structure includes a plurality of laterally relatively spaced vertical column-like structural members and located between the floatation vessels near the top of the structure and the lowermost regions of the structure, and wherein said structural member are arranged to be used as additional means for balasting/loading the support structure
PCT/GB2008/000985 2007-03-22 2008-03-20 Deep water water current turbine installations WO2008114019A2 (en)

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GBGB0705476.0A GB0705476D0 (en) 2007-03-22 2007-03-22 Deep water water current turbine installations

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WO2016164934A1 (en) * 2015-04-09 2016-10-13 Aquantis, Inc. Floating, yawing spar current/tidal turbine
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WO2008114019A3 (en) 2009-02-19
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GB2447774B (en) 2012-05-23
EP2185809A2 (en) 2010-05-19
GB0705476D0 (en) 2007-05-02

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