Patent Publication Number: US-2017356417-A1

Title: Adaptive hydroelectric turbine system

Description:
FIELD OF THE INVENTION 
     The present invention is concerned with a hydroelectric turbine system, for example comprising a hydroelectric turbine mounted on and supported by a base for location on the seabed or other underwater substrate, the base including four ground contacting feet in order to provided improved support and stability to the system, the base additionally being adapted to ensure that all four of the feet contact the seabed. 
     BACKGROUND OF THE INVENTION 
     Renewable energy has come to the fore in recent years, with many projects being developed around solar energy, wind energy, and tidal power. Of these alternative forms of energy, tidal power is arguably the most attractive, given that tidal flows are entirely predictable and constant, unlike wind or solar energy which are relatively intermittent and therefore less dependable. 
     However, harnessing tidal energy does provide its own challenges, in particular with respect to the installation and maintenance of tidal power generators, for example hydroelectric turbines, which by the very nature of operation must be located in relatively fast flowing tidal currents, and more than likely located on the seabed. 
     It is known to use a “gravity base” which is adapted to be lowered onto the seabed and to remain in position solely due to the weight or load of the combined base and turbine acting on the seabed through a number of seabed contacting feet or legs. A gravity base has the advantage of not requiring any site preparation works prior to deployment. However, during extreme conditions such a gravity base is susceptible to lateral sliding displacement. Such displacement may result in the turbine being incorrectly oriented relative to the prevailing tidal flow, thereby negatively impacting on the power generating capability of the turbine, or may in the event of significant displacement, result in damage to the cabling connecting the turbine to an onshore grid connection via which electrical power is taken from the turbine. 
     A favoured form of gravity base utilises a tripod arrangement having three ground contacting feet, the tripod design ensuring that all three feet will automatically contact the seabed, thus avoiding the need for any remedial operations following the initial deployment, in order to ensure that the feet are fully in contact with the seabed and thus functioning to bear the load of the system. 
     However in addition to the above extreme events, a large number of suitable tidal sites have what are known as “off axis” effects, meaning that the ebb and flow of the tide are not in direct opposition to one another. As a result the axis of rotation of the turbine may be aligned with the tide for one direction, but misaligned when the tide flows in the opposite direction. This may be problematic when using a tripod type base, as the three legs will generally be arranged/oriented to provide maximum stability when the tidal flow is coaxial with the axis of rotation of the turbine, meaning that when the tide changes direction and then flows “off axis” instability may arise. 
     In order to design a base for supporting the turbine which is capable of withstanding these types of issues and which will allow deployment at even more energetic sites, gravity bases are required to get bigger in order to be stable which in turn means the marine equipment needed to install the turbines gets bigger (larger deployment vessels, bigger winches, deeper draught needed at quaysides for mobilisation). This results in more weight which then means more ballast which adds material costs, in addition to increased costs for larger lifting and other equipment necessary to transport and deploy the systems. It is also more difficult to find existing equipment that can handle the increased sizes. 
     It is therefore an object of the present invention to overcome the above mentioned problems of the prior art. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided an adaptive hydroelectric turbine system comprising a base comprising four ground contacting feet; characterised in that at least one of the feet is displaceable relative to the base. 
     Preferably, displacement of the at least one foot is in the form of rotation and/or translation of the foot relative to the base. 
     Preferably, displacement of the at least one foot is facilitated by a coupling about which the at least one foot is displaceable. 
     Preferably, the coupling comprises a pivot. 
     Preferably, the coupling comprises a pivotless flexible member. 
     Preferably, the coupling is operable to undergo plastic deformation in order to facilitate the displacement of the at least one foot. 
     Preferably, the coupling is adapted to generate a reaction moment responsive to displacement of the at least one foot relative to the base. 
     Preferably, the coupling is adapted to temporarily enable displacement of the at least one foot relative to the base. 
     Preferably, the system comprises an immobiliser adapted to allow the at least one displaceable foot to be immobilised relative to the base. 
     Preferably, the immobiliser is defined by the coupling. 
     Preferably, the immobiliser comprises a curable component. 
     Preferably, a pair of feet are displaceable relative to the base while being fixed relative to one another. 
     Preferably, the base comprises a main frame on which at least a pair of the feet are provided, and a subframe on which the at least one displaceable foot is provided, the subframe being displaceable relative to the main frame. 
     Preferably, the subframe is displaceable about an axis which extends substantially perpendicular to an axis of rotation of a hydroelectric turbine when mounted to the base. 
     Preferably, the subframe is displaceable about an axis which extends substantially parallel to an axis of rotation of a hydroelectric turbine when mounted to the base. 
     Preferably, the subframe comprises a cross member pivotably mounted to the main frame and from which subframe the at least one displaceable foot extends. 
     Preferably, the base comprises four legs, a free end of each leg being defined by one of the ground contacting feet. 
     Preferably, the system comprises a restrictor operable to limit the range of movement of the at least one foot relative to the base. 
     Preferably, the restrictor is adapted to limit rotational displacement of the at least one foot. 
     According to a second aspect of the present invention there is provided a method of deploying a hydroelectric turbine system on a non uniform underwater surface, the method comprising the steps of:
         lowering a base onto the underwater surface, the base having four ground contacting feet;   permitting at least one of the feet to be displaced relative to the base such that all of the feet contact the underwater surface.       

     Preferably, the method comprises, in the step of permitting displacement of at least one of the feet, permitting the at least one foot to rotate about an axis. 
     Preferably, the method comprises temporarily permitting displacement of at least one of the feet. 
     Preferably, the method comprises the step of immobilising the at least one displaceable foot, relative to the base, following contact of all of the feet with the underwater surface. 
     Preferably, the method comprises the step of permitting a curable component to set such as to immobilise the at least one displaceable foot. 
     As used herein, the term “hydroelectric turbine system” is intended to cover a system comprising a tidal turbine for the generation of electricity, and/or one or more electrical components for managing and/or conditioning the generation of electricity from one or more of such tidal turbines, and which turbine system may be mounted on a base for location on an underwater deployment substrate such as the seabed. 
     As used herein, the term “foot” is intended to mean a ground contacting load bearing element, and may be formed at the otherwise free end of a leg, whether integrally with the leg as a simple free end of the leg, or through some form of articulated connection allowing the foot to move relative to the leg, and may alternatively take the form of one or more spikes or similar ground penetrating elements. 
     As used herein, the term “coupling” is intended to mean a connection between two or more parts of a system, which coupling may incorporate two or more elements, rigid or otherwise, which are articulated relative to one another, in addition to a single flexible or otherwise deformable element which permits relative movement between the two parts of the system. 
     As used herein, the term “pivot” is intended to mean a conventional pivot defined by a single axis of rotation, in addition to a virtual pivot which may be defined by two or more physical pivot axes which together define a virtual pivot point, which may be fixed or movable, in addition to covering any other arrangement which allows rotation of one element relative to another. 
     As used herein, the term “temporarily” is intended to mean for a short period of time relative to the overall working life of a component which may be in use for years or decades, and for example may cover a period of hours or days. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the accompanying drawings, in which; 
         FIG. 1  illustrates a perspective view of a hydroelectric turbine system according to a preferred embodiment of the present invention; 
         FIG. 2  illustrates a perspective view of an alternative embodiment of a hydroelectric turbine system according to the present invention; 
         FIG. 3  illustrates a front elevation of the hydroelectric turbine system according to the embodiment illustrated in  FIG. 1 ; 
         FIG. 4  illustrates a portion of the hydroelectric turbine system of  FIG. 3  showing an optional component which may be provided; and 
         FIG. 5  illustrates one of four ground contacting feet forming part of the hydroelectric turbine system of the embodiment of either  FIG. 1  or  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring now to  FIGS. 1 and 3 to 5  of the accompanying drawings there is illustrated a hydroelectric turbine system according to an embodiment of the present invention, and generally indicated as  10 . The hydroelectric turbine system  10  comprises a hydroelectric turbine  12  mounted on a gravity base  14  which is intended to be deployed onto the seabed or other underwater support substrate, in order to support the turbine  12  in a manner which permits the turbine  12  to generate electricity in response to the tidal flow of water through the turbine  12 , preferably in a bidirectional manner. The invention is not however intended to be limited to use with a gravity base, although this is the preferred embodiment. The turbine  14  could also be omitted in place of one or more electrical components (not shown) for processing and/or conditioning electricity generated by one or more of the turbines  14 , for example when provided in an array, and for the purposes of the following description and claims the term “turbine” should be construed as covering such components. 
     While the turbine  12  illustrated is of the type having a shaftless rotor housed within a stator for rotation relative thereto, it will be appreciated from the following description of the configuration and operation of the system  10  that the turbine  12  may be of any other suitable form, for example having a central support shaft, an exposed or non shrouded propeller type rotor, or any other suitable alternative. Similarly it will be appreciated that while the base  14  is shown of a particular configuration of interconnected frame members  20  carrying a pair of uprights  22  between which the turbine  12  may be mounted, it will be appreciated from the following description that the base  14  may be of any other suitable configuration once certain features and functionality are embodied therein, as hereinafter described, and the base  14  may be employed to carry hardware other than the turbine  12 , for example one or more components (not shown) involved with the generation, conditioning, transmission, and distribution of electricity. 
     The base  14  comprises four ground contacting feet  24 ,  24 ′ at least one of which, and in the embodiment illustrated a pair  24  of which are displaceable relative to the remainder of the base  14 , and in particular relative to the remaining two fixed feet  24 ′. The ability of at least one of the feet  24  to be displaced relative to the remainder of the base  14  ensures that all four feet  24 ,  24 ′ will contact the seabed or other underwater support substrate, in order to ensure that all four feet  24 ,  24 ′ play a load bearing roll in supporting the turbine  12  and providing enhanced stability to the overall system  10 , regardless of the presence of off axis or other destabilising effects such as extreme weather events or the like. 
     In the embodiment illustrated each foot  24 ,  24 ′ is provided on the underside of a corresponding leg  26 . In the embodiment illustrated each foot  24 ,  24 ′ is defined by an underside of the respective leg  26 , although it will be appreciated that one or more of the feet  24 ,  24 ′ may be provided as a components separate from the respective leg  26  and optionally articulated relative thereto. In addition one or more of the feet  24 ,  24 ′ may include one or more spikes or other ground engaging or penetrating features (not shown) to reduce or eliminate unintended sliding displacement of the base  14  along the seabed or other underwater substrate, for example as illustrated in  FIG. 5 . 
     In the embodiment illustrated the base  14  comprises a main frame  28  comprising a triangular arrangement of the frame members  20  and including a pair of the legs  26 , at an underside of each of which is one of the fixed feet  24 ′. The base  14  further comprises a sub frame  30  comprising a cross member  32  provided at either end of which is one of the legs  26 , the underside of each of which defines one of the displaceable feet  24 . The sub frame  30  is pivotally or otherwise mounted to the main frame  28 , in order to be displaceable relative to the main frame  28 , whether through rotation, translation, or a combination thereof. In the preferred embodiment the sub frame  28  is pivotally mounted on a stub axle  34  projecting from an apex of the main frame  28 . One or more bearings (not shown) may be provided between the sub frame  30  and main frame  28  in order to reduce friction during relative displacement. The sub frame  30 , in the embodiment illustrated, is rotatable about an axis, as defined by the stub axle  34 , which extends substantially perpendicular to an axis of rotation of the turbine  12  when mounted to the base  14 . It will however be appreciated that the axis displacement of the sub frame  30  may be disposed at any other suitable or desired orientation. 
     While it is beneficial to permit the above described displacement of the pair of feet  24  relative to the remainder of the base  14 , it is preferable to limit the extent of the displacement in order to ensure that the overall system  10  will remain stable once deployed on the seabed. The base  14  may therefore be provided with a restrictor  36  operable to limit the range of movement, in particular rotation, of the sub frame  30  relative to the main frame  28 . While the restrictor  36  may take any suitable form, in the embodiment illustrated the restrictor  36  is in the form of a pair of opposed mechanical stops  38  between which the cross member  32  is captured, and which have a multi faceted surface against which the cross member  32  may come into register as the sub frame  30  rotates from the horizontal position in one or other direction. The stops  38  may be designed to provide a desired range of acceptable displacement, through rotation, of the sub frame  30 . 
     It is also envisaged that the restrictor  36  could be in the form of a curable component which sets after a predetermined period of time in order to immobilise the sub frame  30  relative to the main frame  28 . Thus for example said curable component (not shown) may be designed to allow the system  10  to be deployed onto the seabed or other underwater deployment substrate, whereby the sub frame  30  will undergo rotational displacement relative to the main frame  28  until all four feet  24 ,  24 ′ are in contact with the seabed. At this point the curable component will set, immobilising the sub frame  30  relative to the main frame  28 , in order to provide a rigid connection between the two while ensuring that all four of the feet  24 ,  24 ′ have been allowed to fully contact the seabed and thus fully support the system  10 . 
     It should also be understood that while relative displacement between the main frame  28  and the sub frame  30  is facilitated by the provision of a pivot defined by the stub axle  34 , any other suitable arrangement or design may be employed which permits displacement of one or more of the feet  24  relative to the remainder of the base  14 , in particular the fixed feet  24 ′. For example it is envisaged that a deformable element may be provided between the main frame  28  and the sub frame  30 , and could for example be formed integrally with either of both said components, which deformable element may be designed to undergo plastic or elastic deformation such as to permit the sub frame  30  to be displaced relative to the main frame  28 . Similarly the stub axle  34  could be omitted such that a fixed or non articulated connection exists between the main frame  28  and the sub frame  30 . In such an arrangement the cross member  32 , or portions thereof, may be plastically or elastically deformable in order to permit displacement of one or both of the feet  24  relative to the remainder of the base  14 . 
     Referring now to  FIG. 2  there is illustrated a hydroelectric turbine system according to an alternative embodiment of the present invention, and generally indicated as  110 . In this alternative embodiment like components have been accorded like reference numerals and unless otherwise stated perform a like function. The system  110  comprises a turbine  112  supported on a base  114  which is formed from a plurality of frame members  120 , the base  114  further comprising four legs  126  at the free end of each of which is a foot  124 ,  124 ′. The base  114  comprises a main frame  128  consisting of two of the frame members  120  in a T-shaped configuration, and a sub frame  130  which comprises a cross member  132  at either end of which is provided one of the legs  126 . The sub frame  130  is arranged to undergo rotational displacement relative to the main frame  128  by means of a coupling  134 . Unlike the embodiment illustrated in  FIG. 1  the system  110  of  FIG. 2  is designed such that the sub frame  130  is displaceable about an axis which extends substantially perpendicular to an axis of rotation of the turbine  112  during operation. The system  110  nevertheless embodies the same functionality, allowing one and preferably a pair of the feet  124  to be displaced relative to the remainder of the base  114 , such as to ensure that all four of the feet  124 ,  124 ′ contact the seabed and therefore bear the load of the system  110  during use. 
     The system  10 ,  110  of the present invention therefore provides a means of designing a base  14 ,  114  on which a turbine or other components may be support, and which base  14 ,  114  has four ground contacting feet  24 ,  24 ′,  124 ,  124 ′ which will automatically all contact the seabed in order to provide improved load bearing and stability, while enabling the base  14 ,  114  to be used in the capacity of a gravity base which does not require pre or post deployment site preparation. This provides significant improvements in stability over a tripod or three legged base (not shown), which is more susceptible to sliding displacement along the seabed due to the reduced number of legs, overturning, in particular in the presence of “off axis” effects, and the general instability of a three legged arrangement.