Polymeric wind turbine foundation

Abstract

A buoyant foundation 40 for supporting a wind turbine, the foundation comprising a polymeric outer shell 94; capped by an upper coupling plate 60 for coupling to the transition piece of a wind turbine

Description

The present invention relates to a polymeric wind turbine foundation, particular for use in providing a buoyant foundation for aquatic wind turbines. Background Wind turbines are an established part of the energy infrastructure of many countries. Situations where wind turbines are optimal for energy generation include where they can be located in an aquatic environment, predominantly in coastal and offshore environments. These locations can often have significant airflow, such as due to the difference in temperature between land and sea. To locate a wind turbine in the aquatic environment, hereafter for convenience termed ‘at sea’, two predominant approaches are available: to create a foundation on the seabed or to have a floating foundation, which is typically secured to the seabed by means of tethers. Both these approaches have their merits but ultimately floating foundations provide the wider scope as they are not limited by the sea depth, depending upon the requirement for and type of tether used. The technology for floating structures of significant size has been developed particularly for oil platforms, oil rigs and the like and thus is well established. A floating steel structure is created, floated into position and then ballasted to one extent or another and secured by tethers. A tether is a substantial cable linking the floating structure to a foundation on the seabed so as to limit, primarily, the lateral movement of the floating structure. In current situations floating structures are typically bespoke designs but with the preparation of wind turbines there is an increasing need for the potential for mass production. In addition, floating structures have tended to be intended for use for a limited duration and hence can be protected by anodic protection or by painting. These methods of protection require ongoing maintenance and for a structure where the absence of corrosion may be more important than the absence of fouling this provides a considerable overhead particularly for wind turbine farms where many hundreds of installations are present. There is therefore a need to reduce the amount of preventative maintenance required. Relevant prior art disclosures include: CN114802623A discloses a floating body for floating type offshore wind power generation equipment utilising plastic pipes. CN112722179A discloses a buoy suitable for a floating type wind turbine generator comprising plastic support elements, in a plurality of glass fibre reinforced plastic foam sandwich units in which multiple glass fibre reinforced plastic foam sandwich units are installed on a hollow metal steel frame. CN215908001U discloses a hybrid buoy structure suitable for a floating fan foundation. 5 CN114033620A discloses a floating type wind power device supported using air bags. There is therefore a need for an improved or alternative foundation for wind turbines which addresses the aforementioned problems. 10 The present invention The present invention in its various aspects is as set out in the appended claims. The present invention provides: A buoyant foundation for supporting a wind turbine, the foundation comprising: a polymeric outer shell; capped by an, in use, upper coupling plate for coupling to a wind turbine support structure; a steel core secured inside the polymeric shell and joined to the coupling plate; a hermetically sealed void between the polymeric shell and the steel core. Advantageously, the foundation provides a robust and low maintenance foundation suitable for attaching to a plurality of different structures to be supported combining both buoyancy and stability due to the combination of steel core and sealed void. Preferably the polymeric outer shell of the foundation is comprised of a thermoplastic. Preferably the thermoplastic is constructed of an injection moulded thermoplastic or an additive manufacture thermoplastic. Preferably the polymeric outer shell of the present invention is made by injection moulding or additive manufacture. Preferably that manufacture is carried out using said thermoplastic. More preferably the polymeric outer shell of the present invention is made by additive manufacture using a thermoplastic. An advantage of thermoplastic is it is quickly and rapidly formed into the polymeric outer shell suitable for the present invention. Advantageously thermoplastic is generally resilient and capable of deformation under load rather than cracking or breaking. Additive manufacture enables the use of multi-materials and polymer blending in different areas of the structure, allowing for greater specificity at certain points, e.g. at the polymer to steel interface. The use of automated fast additive manufacturing printers, advantageously increases speed and reduces cost. It also allows the polymeric part of the foundation to be consolidated into a single part with one assembly, reducing the risk of faulty construction or component failure. This eliminates the need for assembly altogether, reducing cost and streamlining the manufacture process, while increasing efficiency. Additively manufactured parts have also been found to have superior mechanical properties compared to the conventionally manufactured counterparts due, in part, to the microstructural features that can be achieved. Additive manufacture causes a reduction in waste as material is only deposited where it is needed. Additive manufacture allows for the direct use of recycled materials, further reducing waste. As a result, additive manufacture has the potential to greatly reduce manufacturing costs and help protect the environment. Additive manufacture allows for a lower energy consumption as the process generally uses less energy than traditional manufacturing processes. Injection moulding enables the polymeric outer shells to be mass produced as a move away from the bespoke structures currently used allowing for mass production. Injection moulding is faster, allowing for shorter manufacture times. Preferably the thermoplastic of the foundation comprises one or more of Polyethylene Terephthalate (PET or PETE); High-Density Polyethylene (HDPE); Polyvinyl Chloride (PVC or Vinyl); Polypropylene (PP); Acrylonitrile Butadiene Styrene (ABS); Polycarbonate; Polyethylene. An advantage of these particular thermoplastics is that they are resistant to the buildup of sea life, are particularly resilient and deformable and are suitable for injection moulding or additive manufacture. Additionally, the use of thermoplastic allows for manufacture using either additive manufacture or injection moulding allowing for the same component to be manufactured using different methods, including changing manufacture method at different times in the lifecycle of the design. For example, designs undergoing rapid growth in popularity can have rate of manufacture increase by switching to injection moulding whereas legacy designs can be supported with additive manufacturing without requiring redesign. This is particularly relevant for replacement parts. More preferably the foundation is comprised of the thermoplastic polyethylene or polypropylene. These particular thermoplastics are particularly robust and resistant to the buildup of sea life. They also remain flexible at low temperatures, such as Arctic waters and so are not prone to cracking or breaking in normal use. To the extent that they may be externally impacted they will deform rather than break, and by use of internal air pressure can be reformed back into their original shape when out of the water. Preferably the foundation comprises fibre reinforced thermoplastic. The use of fibre reinforcement reduces the possibility of tears in the polymeric outer shell such as along mould lines arising from injection moulding. The use of fibre reinforcement reduces the possibility of tears in the polymeric outer shell such as along layer lines arising from additive manufacture. Additive manufacture and injection moulding are preferable over a traditional glass fibre thermoset plastic construction because it reduces the volume of manual work required by skilled workers. Additive manufacture is most preferred in this respect because it provides the ability to change the polymer composition where needed, can be automated, has superior mechanical properties including reduced component failure and also produces less waste whilst using less energy. Preferably the foundation comprises fibre reinforced thermoplastic are reinforced with one or more of glass fibre, carbon fibre, aramid fibre, nylon fibre, cellulose fibre and metal fibre. These fibres are particularly suitable in providing high tensile strength and compatibility with thermoplastics. Particularly useful are nylon such as nylon 6:6 as this also being a thermoplastic can partly melt into the parent thermoplastic, such as polyethylene to provide high integration of the fibres into the overall structure and improve strength. More preferably the foundation comprises fibre reinforced thermoplastic reinforced with glass fibre. Glass fibre is particularly useful due to its high tensile strength. Alternatively, it is preferable the foundation comprises fibre reinforced thermoplastic reinforced with metal fibre. Preferably the metal fibre is selected from copper, zinc or alloy based thereupon and stainless steel. The use of metal reinforcement fibres of the types mentioned are particular useful as they hinder biological contamination and buildup on the polymeric outer shell as metal irons slowly leach out all the fibres and provide an anti-contamination effect. In addition, they also, when present on the surface of the outer shell can provide some degree of electrolytic protection for the steel part of the structure. Preferably the steel core of the foundation is joined to the coupling plate and serves to sandwich a portion of the outer shell in. This provides a hermetic seal to the outer shell. This provides a strong and convenient joint between the buoyant element, the outer shell, and the ballasting elements of the steel core. It also enables simple and rapid construction of the overall foundation. Preferably the polymeric outer shell of the foundation is one of more of spheroidal, cylindrical or frustoconical. These shapes are particularly useful, in particular with thermoplastics as they provide minimum surface to volume and therefore to the extent that surface contamination occurs it creates a small overall effect. Preferably the foundation’s outer shell is spheroidal. This broader shape provides the optimum hollow surface area, i.e. the optimisation of surface area to volume. It also makes best use of the resilience, such as of thermoplastics, particularly when the void is filled with gas under pressure. Preferably the foundation’s outer shell is oblate spheroidal. This shape allows the advantages of a spheroid and provides greater stability due to the increased resistance, or drag, the shape will exert when moving through the water caused by the effects of wave or wind action on the supported structure. Preferably the foundation’s outer shell comprises a plurality of anchor points integrally formed into the shell. The anchoring points, which may be in any configuration, are embedded into the outer shell and therefore the upward force due to the buoyancy of the foundation is directly connected to the restraining force of tethers, such as may be attached to the seabed in use so as to avoid placing stress on any individual intermediate components. Preferably the hermetically sealed void of the foundation is, in use filled with one or more of, air, an inert gas, such as nitrogen, or expanded polystyrene. Whilst a vacuum may be suitable, the use of air or other gases enables some degree of pressure to be placed in the void of the outer shell to effectively strengthen the outer shell against external forces and allow the outer shell to be constructed of thinner material. The use of expanded polystyrene avoids the potential for flooding due to leakage should this occur. Preferably the suggested invention is a foundation for a wind turbine. The ability to mass-produce the foundations of the present invention makes them in particular useful for wind turbines in large floating arrays. The invention can be used as part of a support structure for a wind turbine comprising one or more of the foundations, linked by a steel structure. The wind turbine can be mounted to the coupling plates of one of the foundations. This enables the foundation to be used for larger wind turbines or in locations where increased stability is required. The ability to link the foundations enables more stable structures to be created such as trigonal arrangement, square arrangement or pentagonal arrangement, which provide a wider and hence more stable base for supporting a structure, such as a wind turbine. Preferably the buoyant foundation wherein the steel structure is a structure lateral to the, in use, level of the foundations, perpendicular to the tower. The use of planar structures provides inherent stability without the requirement for tethers to provide lateral stability, such as a wind turbine. Tethers will normally be required for preventing lateral movement. Preferably the support structure further comprises, in use, vertical steel stanchions for connecting to and securing a base of a wind turbine. This enables the foundations to be spread out, such as in the aforementioned planar configurations at such a level that they are clear of the hulls of passing boats and connected to wind turbine vertically so that what is below the water corresponds to the position and what is above. This aids navigation reduces the possibility of impact of a boat upon the foundations and the consequent potential damage. A wind turbine supported by one or more of the foundations described. A preferred use of the foundations the present invention is with a wind turbine is the foundations can be readily mass produced and therefore suitable for use in wind farms, such as wind farms at sea. In particular, such wind turbines are typically intended to remain in place for many years and the resiliency and resistance to contamination of the foundations of the present invention makes them particularly suitable for this use. Preferably the buoyant foundation is formed as a single piece of plastic. This prevents sea life becoming imbedded in cracks, crevasses or seamlines, which is not desirable. This additionally prevents the foundations from accumulating dirt. Preferably the foundations are a standard size allowing for mass production. If the mass to be supported is too great for a single buoyant foundation, these buoyant foundations can be used in greater numbers, attached together as previously described in the required formation. Three foundations usually being sufficient to maintain the structure upright. If the innovative buoyant foundation is to be used to support a platform the preferred shape of the modular elements is square. Alternatively, the shape of the modular elements is an equilateral triangle. The points of the shape of the modular element correspond with the location of a foundation. This is advantageous as it allows for a large range of platform sizes, using the same components. Additional innovative buoyant foundations may be added to provide the required buoyancy. This is further advantageous as it allows for the reusing of components between designs, which avoids creating waste in manufacturing. Preferably the modular elements can be assembled, disassembled and reassembled without degradation of the elements. Additional modular elements can be added or subtracted if necessary. Preferably the foundations are resistant to changes in temperature and long-term exposure to both high and low temperature associated with the changing seasons. Nothing of this size has been manufactured by polymeric additive manufacture at scale before. Nothing of this size has been manufactured by polymeric injection moulding at scale before. Drawings The present invention is illustrated by means of the following drawings in which like features are designated with like numerals. The figures provide: figure 1 shows an illustrative wind turbine and support structure founded upon by four polymeric wind turbine foundations of the present invention to support a multi tower turbine; figure 2 shows an alternative form of support structure constructed from a plurality of polymeric wind turbine foundations of the present invention for a single tower wind turbine; figure 3 shows a wind turbine foundation of the present invention in perspective view; figure 4 shows a wind turbine foundation of figures 2 in side view and indicating the location which a cross section is taken; figure 5 shows a wind turbine foundation of figures 2 and 3 where the cross section indicated in figure 4 is provided; figure 6 shows a frustoconical wind turbine foundation in the present invention being an alternative embodiment of that shown in previous figures; figure 7a shows an oblate spheroid wind turbine foundation of the present invention being an alternative embodiment that shown in the previous figures. figure 7b shows an oblate spheroid wind turbine foundation of the present invention being the same embodiment as depicted in the previous figure 7a. figure 8 shows 4 spheroid foundations being used to support a platform associated with an offshore wind array, being used to house substations, transformers, or control equipment. The features of the drawings are listed as follows: 10 an illustrative use of the present invention; 20 wind turbine; 30 support structure; 40 spheroidal wind turbine foundation; 50 wind turbine support structure and turbine foundations; 60 foundation coupling plate; 70 foundation coupling fixings; 72 coupling fixing threaded rod; 74 coupling fixing securing feature in the form of a hexagonal nut; 80 anchor point, illustrative example; 90 polymeric base; 92 interface between polymeric base and coupling plate; 94 wall of polymeric base; 100 buoyancy void; 110 steel core; 120 ballast; 140 frustoconical wind turbine foundation; 142 planar base of frustoconical foundation; 144 tapered sides of frustoconical foundation; 146 planar top face of frustoconical foundation; 240 cylindrical, disc-like, oblate spheroid, wind turbine foundation; 242 base of cylindrical wind turbine foundation; 244 sides of cylindrical wind turbine foundation; 246 planar top face of frustoconical foundation; 310 further illustrative use of the present invention; 316 platform; 318 supported structure; and 320 lateral adjunct of supported structure. Specific description Figure 1 depicts a wind turbine, support structure and foundations. The wind turbine being comprised of 4 supporting towers, nacelle, hub and a plurality of blades. Each buoyant foundation is held via steelwork at the corners of the square structure. When in use the buoyant foundations will be completely submerged by the weight of the supported load and the force exerted by the catenary cables. There are a number of anchor points to which the cables may be attached to each structure. Each buoyant foundation has four anchor points. The anchor points are ‘C’-shaped toroidal segments with circular cross-section. In use, as depicted in the image; the nacelle is above the tower; the tower is above the support structure; the support structure is above the foundations. The blades above the support structure. The nacelle contains the hub. The blades connect to the hub. The hub and blades can rotate. In a full rotation of a blade, at the highest point the blade is entirely above the tower at the lowest point the blade is largely at the same height as the tower. The nacelle being an ellipsoid. The ellipsoid being longer in the of the axis of rotation of the hub than any axis perpendicular to the axis of rotation. The plurality of blades being three blades. The blades equidistantly attached to the hub of the wind turbine. The blades pointing outwards from the hub of the wind turbine. The blades being elongate. The blades being triangular. The tower of the wind turbine being comprised of a set of beams, each beam being an elongate cylinder, the tower comprising four beams. Each beam connects to the nacelle. Each beam connects to the support structure. The beams are the same length. The beams are the same thickness. The beams are all the same size. The beams taper together as they ascend, such that the beams are more proximal to each other where the beams connect to the nacelle than the beams are proximal to each other where the beams connect to the support structure. The tower comprising four beams. The beams tapering at the same angle. The angle of the slope of the beams relative to the tower being the same angle however sloping in different directions. The tower being vertical. The tower overall having no slope. The support structure being comprised of stanchions and crossbars. The support structure comprising four stanchions and four crossbars. The stanchions are cylinders. The crossbars cylinders. The stanchions are all the same size. The crossbars are all the same size. The stanchions are vertical. The crossbars are horizontal. Each stanchion is connected to two crossbars. Each crossbar is connected to two stanchions. The centrelines of the cylinders of the crossbars are parallel or perpendicular. Each cylinder of the crossbar having one other crossbar which it is parallel to and two others that is perpendicular to. The centrelines of the cylinders of the crossbars share a plane. The beams of the tower are connected to the stanchions of the support structure. The lower bases of the beams of the towers enter the to the upper bases of the stanchions of the support structure. The bases of the crossbars enter the curved surface of the stanchions. The overlapping portions of the cylinders as described reflecting the connection between parts forming a single object. The cylinders of the stanchions having greater radius than the cylinders of the crossbars or the beams. The cylinders of the crossbars having the same radius as the cylinder of the beams. The beams of the tower being longer than blades of the wind turbine. The blades of the wind turbine being longer than the stanchions of the support structure. The stanchions of the support structure being longer than the crossbars of the support structure. The support structure connected to the wind turbine foundations; The wind turbine foundations being spheroidal; The wind turbine foundations having the shape of a sphere. The figure depicting four foundations. The spheres of the foundations connecting to the lower bases of the stanchions. Each stanchion is connected to one foundation. Each foundation is connected to one stanchion. The foundations do not touch one another. The connectors having equal length. The connectors sharing a plane. The connectors form the edges of a square shape. The stanchions are located on the points of the square. The foundations have anchor points. Each foundation has four anchor points. The anchor points are ‘C’-shaped toroidal segments with circular cross-section. The anchor points are attached to the foundations at their terminal points, the central portions of the anchor points are unconnected. The anchor points attach to the foundation such that ‘C’ shape of the anchor points share a plane. The shared plane on which that anchor points are situated being the central horizontal cross section of the foundation. The place of the anchor point is perpendicular to the place of the surface of the foundation at the central point of the foundation that is closest to the central point of the anchor point, the centre point of the anchor point being the centre of the ‘C’ shape. Figure 2 depicts wind turbine support structure and turbine foundations; Connector. Connectors are cylindrical. The support structure comprising three connectors. Each connector is connected to two foundations. Each foundation is connected to two connectors. The foundations do not touch one another. One foundation additionally has a foundation coupling plate. The foundation coupling plate is connected to the buoyant foundation. The connectors form an equilateral triangle. The foundations are located on the points of the equilateral triangle. The foundation coupling plate is connected to the foundation facing perpendicular to the plane of the equilateral triangle. The coupling plate is connected to foundation coupling fixings. One coupling plate is attached to seven or more foundation coupling fixings. The foundation coupling fixings are elongate fasteners. The coupling will be connected to a transition piece which will link the submerged buoyant foundation and the base of the wind turbine tower. Figure 3 depicts a wind turbine foundation; The wind turbine foundation is similar to the wind turbine foundation in figure 2 with foundation coupling plate. No connectors are depicted. The foundation coupling fixings comprise a coupling fixing threaded rod which is an elongate threaded rod upon which is coupling fixing securing feature in the form of a hexagonal nut, the hexagonal nut slotting onto the threaded rod. The coupling will be connected to a transition piece which will link the submerged buoyant foundation and the base of the wind turbine tower. The polymeric base has four anchor points, three of which are visible in the drawing. This foundation can be used to support a wind turbine on its own if it provides sufficient buoyancy or in combination with other identical buoyant foundations, if necessary, in various shaped structures, see Fig 1 and Fig 2. Figure 4 depicts a wind turbine foundation; The wind turbine embodiment of the wind turbine foundation the same as in figure 3. Where the foundation coupling plate meets the polymeric base is the buoyancy void. The foundation coupling plate circular face is larger than the circular area of the polymeric base which is in contact with the coupling plate. The coupling will be connected to a transition piece which will link the submerged structure and the base of the wind turbine tower. Figure 5 depicts the cross section of a wind turbine foundation; The wind turbine embodiment of the wind turbine foundation the same as in figure 3 and figure 4. The polymeric base is a hollow sphere of uniform wall thickness. In this image the foundation coupling plate is more fully shown. The cylindrical disc foundation coupling plate is shown to be one portion of a larger single metal piece, the larger single metal piece being the steel core. The steel core having a ‘I’ vertical cross-section shape. The steel core having an elongate shape. The steel core being embedded in the foundation. The steel core comprised of three-cylinder portions. The upper most cylinder being a cylindrical disc being the foundation coupling plate for mounting to the transition piece. The lower most cylinder being a cylindrical disc having the same diameter as the cylindrical disc foundation coupling plate. The cylinder that is centre most being elongate. The cylindrical axis of each of the cylinders sharing a line. The polymeric base is encapsulating the lower and central beams of the ‘I’ shape of the steel core. The upper half of the polymeric base, where not filled by the steel core, is filled with air, inert gas or buoyant material such as expanded polystyrene. The lower half of the polymeric base, where not filled by the steel core, is filled with a ballast. The ballast fills the shape of a hemisphere with a portion subtracted, the portion subtracted being the shape of the lower half of the steel core. Figure 6 depicts a frustoconical wind turbine foundation. The wind turbine foundation is a conical frustum. On the upper surface of the conical frustum is the foundation coupling plate. The lower surface conical frustum of the wind turbine foundation has a larger surface are than the surface area of the upper surface of the conical frustum. The sides of the conical frustum taper inwards from the lower face to the upper face. The upper face of the conical frustum is a circle. Lower face of the conical frustum is a circle. The circular upper face of the conical frustum is larger than the foundation coupling plate circular face which is on it. The circular upper face of the conical frustum extends beyond the conical frustum. On the curved side face of the conical frustum of the wind turbine foundation the wind turbine foundation has anchor points. Four anchor points are uniformly and equidistantly situated on the line of the edge circular a cross section of the conical frustum. Three of the anchor points are visible in the diagram. The anchor points face outwards from the centre of the conical frustum such that they do not point out at the slope of the curved surface of the conical frustum instead being at an angle to the surface of the conical frustum. The anchor points all sharing a plane. Figures 7A and 7B depict an oblate spheroid wind turbine foundation. The wind turbine foundation is an oblate spheroid. The oblate spheroid is laterally extended. The polymeric oblate spheroid base is predominantly cylindrical. On the upper circular face of the cylindrical wind turbine foundation is a cylindrical coupling plate. The circular faces of the oblate spheroid wind turbine foundation are larger than the circular face of the cylindrical coupling plate. The coupling will be connected to a transition piece which will link the submerged buoyant foundation and the base of the wind turbine tower. On the curved side face of the oblate spheroid of the wind turbine foundation the wind turbine foundation has anchor points. Four anchor points are uniformly and equidistantly situated around the circumference of the cylinder. The anchor points are situated centrally on the height of the cylinder of the curved surface of the cylinder. The ‘C’ shapes of the anchor points share a plane. The plane of the ‘C’ shape of the anchor points being parallel to the planes of the circular faces of the cylinder. Figure 8 depicts use of the buoyant foundation for an application other than a wind turbine. The drawing depicts a further illustrative use of the present invention. The use illustrated is a floating platform, the platform suitable for being used to house substations, transformers or control equipment. The support structure comprises four elongate cylinders. There are four spheroidal wind turbine foundations. On the lower end of each support structure elongate cylinder is a spheroidal wind turbine foundation. The spheroidal wind turbine foundations are each only attached to one support structure elongate cylinder. On the upper end of the support structure elongate cylinders is a platform. The platform is a square prism. The square prism of the platform has large square faces. The square prism of the platform has a small height. The height of the square prism of the platform is small such that the platform is a square sheet. The side length of the square faces of the square prism are larger than the height of the square prism of the platform. The support structure elongate cylinders each connect to the platform at a point in between the centre of the lower square face platform and the midpoint of the one of the edges of the lower square face. Each of the four elongate cylinders at a point corresponding with a different edge of the lower square face. The four elongate cylinders each corresponding with one of the four edges of the square. The points at which the centre of the upper circular faces of the cylinders meet the platform being closer to the midpoint of one of the edges of the lower square face of the platform than to the centre of the lower square face of the platform. The distance between the centre of the lower square face of the platform and the centre point of the upper circular face of the cylinder that is connected to the platform being the same. The centre points of the upper circular faces of the cylinders that are connected to the platform being points such that if the points were connected, they would be connected to create a square, the square connected having edges at 45 degrees from the edges of the lower square face of the platform. The square bases of the square prism of the platform being horizontal. On the platform is a supported structure, the supported structure being a building. The supported structure taking up the majority of the space on the platform. The supported structure has to overall form of a square prism. The square prism of the supported structure having holes. The supported structure being hollow. The height of square prism of the supported structure is less than the side length of the squares of the square prism. The supported structure having a square upper face. The square upper face of the square prism of the supported structure being the roof of the supported structure. The roof of the supported structure being flat. The roof of the supported structure being square. The roof of the supported structure being parallel to the square surface of the platform. The roof of the supporting structure being a floor. Attached to the square prism of the supported structure is the lateral adjunct of supported structure. The lateral adjunct of supported structure comprising two elongate beams. The lateral adjunct of supported structure comprising a hexagonal prism. The two elongate beams of the lateral adjunct of supported structure supporting the hexagonal prism of the lateral adjunct of supported structure from below. The two elongate beams of the lateral adjunct of supported structure The hexagonal prism of the lateral adjunct of supported structure suitable for landing a helicopter. The hexagonal prism of the lateral adjunct of supported structure suitable for the take-off of a helicopter. The lateral adjunct of supported structure is such that the supported structure has only one plane of symmetry. In all of the diagrams: The foundation coupling plate, foundation coupling fixings, the coupling fixing threaded rod and coupling fixing securing feature in the form of a hexagonal nut all may comprising metal, preferably the metal is steel. The wind turbine foundation, may comprise of plastic. The anchor points may comprise of steel imbedded in the polymeric buoyant foundation and may be internally connected to the steel core by means of a rod, chain or bar. The buoyancy void may be filled with compressed air, inert gas or expanded polystyrene. The steel core may consist of steel. The ballast may comprise a dense material, such as gravel, sand, or solid plastic. The platform and supported structure and lateral adjunct of supported structure may comprise metal, the metal may be steel. 5 The steel components, where connected, may be formed of or welded into, a single piece.

Claims

1. A buoyant foundation for supporting a wind turbine, the foundation comprising: a. a polymeric outer shell;b. capped by an, in use, upper coupling plate for coupling to the transition piece of a wind turbine support structure;c. a steel core secured inside the polymeric shell and joined to the coupling plate;d. a hermetically sealed void between the polymeric shell and the steel core.

2. The foundation of claim 1 wherein the polymeric outer shell is comprised of a thermoplastic, and is preferably an injection moulded thermoplastic or an additive manufacture thermoplastic.

3. The foundation of claim 2 when the thermoplastic comprises one or more of Polyethylene Terephthalate (PET or PETE); High-Density Polyethylene (HDPE); Polyvinyl Chloride (PVC or Vinyl); Polypropylene (PP); Acrylonitrile Butadiene Styrene (ABS); Polycarbonate; Polyethylene.

4. The foundation of claim 3 were in the thermoplastic expect selected from polyethylene or polypropylene.

5. The foundation of claim 3 or claim 4 were in the thermoplastic is fibre reinforced.

6. The foundation of claim 5 when the fibre reinforcement comprises one or more of glass fibre, carbon fibre, aramid fibre, nylon fibre, cellulose fibre and metal fibre.

7. The foundation of claim 6 when the fibre reinforcement comprises glass fibre.

8. The foundation of claim 6 were in the reinforcement fibre comprises metal fibre that metal fibre is selected from copper, zinc or alloy based thereupon and stainless steel.

9. The foundation of any preceding claim wherein the steel core is joined to the coupling plate and serves to sandwich a portion of the outer shell in that during so as to provide a hermetic seal to the outer shell.

10. The foundation of any preceding claim wherein the polymeric outer shell is one of more of spheroidal, oblate spheroid, cylindrical and frustoconical.

11. The foundation of claim 10 wherein the outer shell is spheroidal.

12. The foundation of any preceding claim wherein the outer shell comprises a plurality of anchor points integrally formed into the shell.

13. The foundation of any preceding claim wherein the hermetically sealed void is, in use filled with one or more of, air, an inert gas, such as nitrogen, and expanded polystyrene.

14. The foundation of any preceding claim when the foundation is a foundation for a wind turbine.

15. A support structure for a wind turbine comprising one or more of the foundations of any of claims 1 to 15 linked by a steel structure for supporting a wind turbine coupled to the coupling plates of the one or more foundations.

16. Support structure of claim 16 wherein the structure comprises a plurality the foundations.

17. A wind turbine supported by one or more of the foundations of any of claims 1 to 19.

18. A method of manufacturing the foundation of any preceding claim wherein the polymeric outer shell is constructed by additive manufacture.

19. The method of manufacture of claim 18 when the polymer is a thermoplastic polymer.

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