Water-based platform for a wind turbine

Abstract

Water-based platform for a wind turbine, said water-based platform comprising a foundation element which establishes a stable foundation for the wind turbine on the water and a wind turbine tower connection portion arranged on the foundation element. The water-based platform further comprises: an equipment support structure and equipment for maintaining / servicing the wind turbine. The equipment being supported on the foundation element by the equipment support structure and said equipment support structure being connected to the foundation element such that the entire weight of said equipment supported by the equipment support structure is transferred to the foundation element via said equipment support structure.

Description

[0001] WATER-BASED PLATFORM FOR A WIND TURBINE

[0002] The current invention relates to a water-based platform for a wind turbine, said water-based platform comprising a foundation element which establishes a stable foundation for the wind turbine on the water and a wind turbine tower connection portion arranged on the foundation element.

[0003] Description of related art

[0004] When erecting wind turbines in water-based environments, for example intertidal or offshore environments, it is common to prepare a platform on top of which the wind turbine tower is erected. Such offshore platforms can either be fixed to the seabed if the water depth is not so deep, or they can be floating platforms. For the sake of this specification, the term “water-based platform” is used to cover platforms of both types. It should be noted that water-based platforms can be used in both bodies of fresh water as well as bodies of salt water.

[0005] When repairs or maintenance on water-based wind turbines need to be performed, it is common to sail the necessary maintenance / service equipment out to the wind turbine on a floating vessel, for example a ship, boat, barge, etc. The equipment can then be operated from the vessel. For example, cranes can be operated from such vessels. However, during use it is necessary that the crane is stationary and not affected by the wind or waves of the water. As such, it is necessary to anchor and control the position of the vessel precisely.

[0006] In additional to vessel mounted cranes, up-tower cranes have been developed which can be lifted to the top of the wind turbine tower. The up-tower crane can then perform all the lifting operations without the need for a stationary base, as the wind turbine tower itself functions as the base of the crane.

[0007] Up-tower cranes are typically transported to the wind turbine site in containers. The container is typically a self-contained unit which contains the crane, the crane equipment and the winches necessary to operate the crane. Such a “crane container” can be arranged on a vessel or other form of floating support structure and sailed to the wind turbine. The crane can then be operated from the vessel or other floating support structure via the crane container.

[0008] However, the use of vessels can be expensive and makes the entire operation more complex. Furthermore, the vessel is not free to do other tasks during the entire lifting operation if the container is arranged on the vessel during the lifting operation.

[0009] In a similar manner, other forms of maintenance, service, repair and / or supporting equipment are also needed for maintaining / servicing wind turbines arranged on water-based platforms. For example, blade inspection platforms, repair platforms, blade yokes, blade turning tools, etc. Again, these are typically sailed out to the water-based platform with vessels and have similar issues as described above.

[0010] Summary of the invention

[0011] It is therefore, a first aspect of the current invention to provide for a more flexible use of maintenance / service equipment.

[0012] It is a second aspect of the current invention to reduce the need for vessels during a maintenance / service operation.

[0013] These aspects are provided at least in part by a water-based platform for a wind turbine as mentioned in the opening paragraph, where the water-based platform further comprises: a. an equipment support structure and b. equipment for maintaining / servicing the wind turbine, c. said equipment being supported on the foundation element by the equipment support structure, and d. said equipment support structure being connected to the foundation element such that the entire weight of said equipment supported by the equipment support structure is transferred to the foundation element via said equipment support structure. In this way, large equipment can be supported on the foundation element of the water-based platform even if the equipment overlaps the available surface area of the foundation element.

[0014] This allows a vessel to sail the maintenance / service equipment, for example a crane container, out to the platform, and then move the equipment to the platform. Once the equipment is properly arranged on the platform, the vessel can leave. In this way, the vessel can be used for other tasks while the maintenance / service equipment is operated. The vessel can then come back later to pick up the equipment and move it to another wind turbine platform. In the case of a crane container for example, multiple cranes could be set in motion simultaneously. A single vessel could be sailed out with two or more crane containers. A first crane container can be delivered to a first wind turbine platform and then a second crane container can be delivered to a second wind turbine platform. While the second crane container is being installed, the crane of the first crane container can already be in action on the first wind turbine.

[0015] Some non-limiting examples of equipment for which the current invention is suitable for could for example be a crane container, a blade inspection platform, a repair platform, etc. In some embodiments, said equipment does not include components of the wind turbine itself.

[0016] According to this specification, the term “wind turbine tower connection portion” is understood as a portion of the platform which is arranged so that a wind turbine tower can be connected to it. Since wind turbine towers come in many different designs, the tower connection portion will be specific to the wind turbine arranged on the platform.

[0017] In some embodiments, the equipment support structure is a temporary equipment support structure, and it is detachably attached to the foundation element such that it is removeable from the foundation element when not in use. In some embodiments, the equipment support structure comprises multiple separate component elements which cooperate to support the equipment on the foundation element. In some embodiments at least a portion of said equipment is arranged outside the projected area of the foundation element when seen from above the foundation element. It should be noted that the projected area when seen from above the foundation element is to be understood as the area which the foundation element would vertically project onto the surface of the water where the foundation element is arranged. In certain embodiments, at least a portion of said equipment is arranged outside the outer periphery of the foundation element when seen from above the foundation element. In some embodiments, said equipment is arranged such that a centre of gravity of said equipment is arranged outside the projected area of the foundation element when seen from above the foundation element for at least some of the working configurations of said equipment. In some embodiments, a centre of gravity of said equipment is arranged outside the outer periphery of the foundation element for at least some of the working configurations of said equipment. It should be noted that the phrase “working configurations” should be understood as the working configurations which are intended to be used during a particular maintenance / service procedure at the particular installation site where the equipment is in operation.

[0018] In some embodiments, said equipment support structure comprises a counterweight element which is arranged in or on said equipment such that the centre of gravity of a combination of said equipment and said counterweight element is a) closer to the foundation element than the centre of gravity of said equipment alone or is b) arranged inside the projected area of the foundation element when seen from above. In some embodiments, the counterweight element could be arranged to be adjustable in weight and / or position during operation of said equipment. In some embodiments, the counterweight element could comprise a volume which is fillable with water to increase its weight. In some embodiments, the counterweight element could comprise a volume which is expandable, for example via stretchable side walls.

[0019] In some embodiments the equipment support structure comprises a frame element arranged at least partly underneath said equipment to support said equipment. In some embodiments, said equipment support structure further comprises a support surface supported by said frame element and in that said equipment is arranged on said support surface.

[0020] In some embodiments said frame element is detachably attached to the foundation element. In some embodiments, the frame element is detachably attached to the foundation element via one or more fastening elements which are detachably engaged with corresponding fastening elements on the foundation element. In some embodiments, the corresponding fastening elements on the foundation element comprise bolts used to attach a wind turbine tower to the foundation element.

[0021] In some embodiments, said frame element is arranged to extend from a location on the foundation element to a location away from the foundation element, said location away from the foundation element being further away from the foundation element than a centre of gravity of said equipment. In some embodiments, the frame element does not extend past a centre of gravity of said equipment.

[0022] In some embodiments, the equipment support structure comprises detachable fastening elements arranged between said equipment and the frame element. In some embodiments the frame element comprises a counterweight element such that the centre of gravity of the combination of the frame element and said equipment is arranged inside the projected area of the foundation element.

[0023] In some embodiments, said equipment support structure comprises a tension member which is attached to the foundation element and to the equipment and / or to an element of said equipment support structure, said tension member being arranged to apply a moment to said equipment and / or to said element to counteract a moment due to the centre of gravity of said equipment. In some embodiments, the tension member is connected to a portion of the equipment or to a portion of said element which is closer to the foundation element than a centre of gravity of the equipment. In some embodiments, the tension member is an elongated element which comprises at least a portion which is flexible. In some embodiments, the tension member is connected to an upper portion of the equipment. In some embodiments, the tension member is connected to a portion of the equipment which is arranged vertically above the centre of gravity of the equipment. In some embodiments, the tension member is arranged at an angle of less than 45 degrees to the horizontal. In some embodiments, the tension member is an elongated flexible element, for example a wire, a sling, a cable or a rope. In some embodiments, the tension member has a portion which is wrapped around a portion of the wind turbine tower and / or a portion of the wind turbine tower connection portion.

[0024] In some embodiments, said equipment support structure comprises a compression member which is attached to the foundation element and to the equipment and / or to an element of the equipment support structure, said compression member being arranged to apply a moment to said equipment and / or said element to counteract a moment due to the centre of gravity of the equipment. In some embodiments, the compression member is attached to a portion of the equipment and / or said element which is located further away from the foundation element than a centre of gravity of said equipment. In some embodiments, the compression member is attached to a portion of the foundation element which is arranged underneath the equipment.

[0025] In some embodiments, said equipment is a crane container and said equipment support structure is a crane container support structure. According to this specification, the term “crane container” is used to refer to a form of container to hold a crane and at least some of its associated lifting equipment. In many cases, the crane container is in the form of an ISO shipping container which has been modified to contain the crane and associated lifting equipment. In many cases, the crane container contains one or more lifting winches. In some embodiments, the crane is a self-hoisting crane.

[0026] In some embodiments, the crane container support structure comprises a corner connection mechanism which establishes a detachable fixed connection between a corner of the crane container and the foundation element. In some embodiments, the corner connection mechanism engages with a corner fitting of the crane container. In some embodiments, the corner connection mechanism establishes a detachable fixed connection between two corners of the crane container. In some embodiments, the corner connection mechanism engages with a corner fitting of the crane container at said two corners. In some embodiments, instead of a crane container, a container is provided which has a different purpose than supporting a crane.

[0027] It should be emphasized that the term "comprises / comprising / comprised of" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0028] Brief description of the drawings

[0029] In the following, the invention will be described in greater detail with reference to embodiments shown by the enclosed figures. It should be emphasized that the embodiments shown are used for example purposes only and should not be used to limit the scope of the invention.

[0030] Figure 1 shows a schematic side view of a water-based platform for a wind turbine with a wind turbine tower mounted on it.

[0031] Figure 2 shows a schematic side view of a first embodiment of a water-based platform for a wind turbine according to the invention.

[0032] Figure 3 shows a schematic side view of a second embodiment of a water-based platform for a wind turbine according to the invention.

[0033] Figure 4 shows a schematic side view of a third embodiment of a water-based platform for a wind turbine according to the invention.

[0034] Figure 5 shows a schematic side view of a fourth embodiment of a water-based platform for a wind turbine according to the invention.

[0035] Figure 6 shows a schematic side view of a fifth embodiment of a water-based platform for a wind turbine according to the invention. Figure 7 shows a schematic side view of a sixth embodiment of a water-based platform for a wind turbine according to the invention.

[0036] Figure 8 shows a schematic side view of a seventh embodiment of a water-based platform for a wind turbine according to the invention.

[0037] Figure 9 shows a schematic side view of an eighth embodiment of a water-based platform for a wind turbine according to the invention.

[0038] Figure 10 shows a schematic side view of a ninth embodiment of a water-based platform for a wind turbine according to the invention.

[0039] Figure 11 shows a schematic top view of the embodiment of figure 10.

[0040] Figure 12 shows a schematic side view of a tenth embodiment of a water-based platform for a wind turbine according to the invention.

[0041] Figure 13 shows a schematic top view of the embodiment of figure 12.

[0042] Figure 14 shows a schematic side view of an eleventh embodiment of a waterbased platform for a wind turbine according to the invention.

[0043] Figure 15 shows a schematic top view of the embodiment of figure 14.

[0044] Detailed description of the embodiments

[0045] Figure 1 shows a schematic side view of an example of a water-based platform 1 for a wind turbine. In this figure, only the bottom portion of the wind turbine tower 2 is shown. The water-based platform comprises a foundation element 4 and a wind turbine tower connection portion 6. The foundation element comprises a concrete base portion 8 in the shape of an essentially circular disc (when seen from above) with a tapered top surface 10. The top surface forms a downwards sloping cone like shape. The concrete base portion is supported on the ocean floor (not shown) via concrete pillars 12. The wind turbine tower connection portion 6 is arranged on top of and in the centre of the concrete base portion. Suitable elements (not shown) are provided in the wind turbine tower connection portion to engage with the bottom section of the wind turbine tower. Such elements are often bolts protruding upwardly from the tower connection portion which engage with holes in a flange on the bottom of the tower section. Nuts hold the flange in place.

[0046] Water-based platforms as described here, are well known in the art. As such, more details will not be provided here. However, it should be noted, that water-based platforms can come in all shapes and sizes, as well as many different forms. For example, some are supported on the ocean floor via rigid elements, while others are floating on the water surface. In some cases, they could also be supported via semisubmerged platforms. The current invention is able to work with all types of waterbased platforms. Some platforms comprise a single cylindrical element with a circular outer periphery and other platforms can comprise more complex shapes. Some platforms have multiple circular portions connected together by connector arms. Different platforms are known in the art.

[0047] Figure 2 schematically illustrates a first embodiment of a water-based platform according to the invention. Here a water-based platform 1 is arranged, of the kind shown in figure 1. In this embodiment, a crane container 20 has been added to the platform. The crane container is of the kind which is well known in the art, and it won’t be described in detail here. Applicant’s own prior applications, published as W02020 / 201237 and WO2020 / 221716 disclose good examples and are incorporated by reference.

[0048] In this particular embodiment, the crane container is a standard 40’ shipping container of the kind known in the art. The container has been modified to contain an up-tower crane as well as relevant lifting equipment, for example winches. Typically, the winches will be located at the end of the container which is located away from the wind turbine tower. This makes the end of the container which is located away from the wind turbine tower heavier than the end of the container which is located closer to the wind turbine tower. This means that the centre of gravity 22 of the container is located further away from the tower than the geometric centre of the container. To support the crane container during a crane operation, a frame element 24 has been attached to the concrete base portion 8 of the foundation element 4 via bolts 26. Suitable nut elements (not shown) are arranged in the top surface 10 of the concrete base portion. It should be noted that other forms of fastening elements could be used to connect the frame element to the top surface of the concrete base portion. For example, eye bolts or other forms of closed loops could be arranged on the surface which engage with suitable hooks on the frame element. Or instead of nuts on the concrete base portion, bolts could extend out of the base portion which engage with holes in the frame element. In this embodiment, the frame element extends outwardly from the concrete base portion and extends outwardly past the outer periphery 14 of the concrete base portion such that the outer portion 28 of the frame element is arranged over the water and is not supported by the concrete base portion, other than via the rest of the frame element.

[0049] The frame element also extends out past the centre of gravity 22 of the crane container. In this way, the crane container is supported by the frame element and does not tip into the water. It should be noted that typically, the weight of the crane container is larger than the weight of the crane and load, and therefore the crane container will not be lifted during a typical lifting operation. As such, the crane container does not have to be fixed to the frame element. However, to provide extra security, in the current embodiment, the crane container is detachably fastened to the frame element as well via fastening elements (not shown). In this embodiment, the fastening elements secure the crane container in a horizontal direction to prevent the crane container from sliding along the frame element during a lifting operation and in a vertical direction to prevent the crane container from lifting up. However, within the scope of the current invention, different types of engagements between the frame element and the crane container could be provided. In certain cases, standard corner fittings (not shown) of the container could be used to engage with corner fitting engagement elements (not shown) on the frame element.

[0050] It should be noted that in the current embodiment (and in other embodiments disclosed herein) the end of the crane container, which is closest to the tower, is spaced away from the tower by about 2m. This allows doors (not shown) at the end of the crane container to open. This allows the crane to exit the container at that end. However, instead of providing doors to allow the crane to slide out of the container in a horizontal direction, other forms of mechanism could be provided which lift the crane vertically out of the container. In this case, there would be less need to open doors at the end of the container and the container could be placed closer to the tower itself.

[0051] Figure 3 shows a second embodiment of a water-based platform according to the invention. In this embodiment a “shorter” frame element 40 is provided. The frame element is still attached to the sloping top surface 10 of the concrete base portion 8 of the foundation element 4. However, in this case, the frame element does not extend out past the periphery 14 of the foundation element. Since the centre of gravity 22 of the crane container 20 is located further out than the end portion 42 of the frame element, the crane container 20 will want to tip downwardly about the end 42 of the frame element. However, to hold the crane container in place, a tension member 44 is provided. The tension member 44 holds the crane container against the foundation element and the frame element 40. In this way, strong fastening elements between the frame element and the concrete base portion are not needed as much, since the tension member will be holding the crane container in place, and hence, also the frame element. However, for the sake of security, the frame element 40 can still be attached to the concrete base portion via suitable fasteners (not shown).

[0052] The tension member could be a wire, a chain, a belt, etc. A first end 46 of the tension member is attached to a portion 48 of the crane container which is located between the centre of gravity 22 of the crane container and the tower connection portion 4 of the platform. The second end 50 of the tension member is attached to the foundation element. In this embodiment, the tension member could be arranged to connect to a shackle or other loop like element (not shown) on the top surface of the concrete base portion. The tension member, when under tension, will apply a moment M1 to the crane container about the end portion 42 of the frame element 40 which will counter the moment M2 which is caused by the centre of gravity 22 of the crane container 20 about the same end portion 42 of the frame element. In one embodiment (not shown), the tension member could be in the form of a corner fitting engaging member which engages with a corner fitting of the container.

[0053] Figure 4 shows a third embodiment of a water-based platform according to the invention. This embodiment is very similar to the embodiment of figure 3, however, instead of providing a tension member which engages with the top surface 10 of the concrete base portion 8, a tension member 60 is provided which is wrapped around the tower connection portion 6. This could for example be a wire with a first end 62 which is connected to one top corner 64 of the crane container and a second end (hidden) which is connected to an opposite top corner (hidden) of the crane container. The wire is wrapped around the tower connection portion. In this way, a similar support will be provided as in the embodiment of figure 3. However, in this case, it could be arranged such that no extra fasteners need to be provided on the concrete base portion, but the wire could just stay in place due to friction.

[0054] Figure 5 shows a fourth embodiment of a water-based platform according to the invention. In this embodiment, a frame element 40 is provided which is similar to the one in figures 3 and 4. The frame element is a short frame element which does not extend out past the centre of gravity 22 of the crane container. Hence, the crane container will want to tip over the end 42 of the frame element via the moment M2 due to the centre of gravity of the crane container. However, in this embodiment, a first set of fastening elements 80 are provided between the frame element 40 and the concrete base portion 8 and a second set of fastening element 82 are provided between the frame element and the crane container. In this example, the second set of fastening elements engage with the bottom surface of the crane container. However, the second set of fastening elements could be provided in a different manner. For example, a tension element, similar to the one in figure 3 could be attached between the crane container and the frame element.

[0055] Figure 6 shows a fifth embodiment of a water-based platform according to the current invention. This embodiment is also similar to the above-described embodiments, except that instead of a frame element which extends under a certain length of the crane container, in this embodiment an inside edge 90 of the container is supported on the top surface 10 of the concrete base portion 8. Then a compression member 92, in the form of a metal tube construction is arranged between a bottom surface 94 of the crane container and one of the concrete pillars 12 of the foundation element. In another embodiment (not shown), the compression member is arranged between the bottom surface of the crane container and the concrete base portion of the foundation element. The metal tube construction is arranged at a point 96 of the crane container which is arranged further away from the tower connection portion 6 than the centre of gravity 22 of the crane container. In this way, the crane container is stably supported on the foundation element.

[0056] Figure 7 illustrates a different concept than the previous embodiments. A frame element 40 is provided between the concrete base portion 8 and the crane container 20. Again, it is a short frame element which does not extend past the periphery of the concrete base portion or past the centre of gravity 22’ of the crane container. A counterweight element 100 is placed in the front end 102 of the crane container. Depending on the weight of the counterweight element, the centre of gravity 22 of the combined crane container and counterweight element will displace forward to end at a new centre of gravity 22” which is located between the tower connection portion and the end 42 of the frame element 40. In this way, the moment generated by the centre of gravity of the crane container will not want to tip the container into the water but will hold the container securely on the frame element.

[0057] In another embodiment (not shown), the counterweight element could be displaceable in a horizontal direction. For example, it could be moved from a location further away from the tower connection portion to a position closer to the tower connection portion. In this way, the centre of gravity will move inwardly. This could be relevant to take into account as the crane itself is stored in the crane container before it is lifted out of the crane container. There might not be room for a counterweight at the inner end of the container. However, once the crane is lifted out of the container, the counterweight can be moved in towards the tower connection portion to balance the crane container on the foundation element / frame element.

[0058] It can also be noted that for containers which have container mounted winches, as disclosed in applicant’s co-pending applications described above, during the operation to lift the crane out of the container, the winches will be pulling down on wires which are arranged at the nacelle of the wind turbine tower. Since the winches are pulling the wires down, the wires will likewise be applying a force to the winches which will lift the winches upwardly. Hence, if the winches are arranged in the outer end of the container, then the outer end of the container will be lifted up during the operation to lift the crane out of the container. Hence, it will be possible to move the counterweight from an outer position to an inner position during the lifting operation since the wires will be helping to support the outer end of the crane container. It should be noted that in some embodiments, the wires will leave the crane container via exit sheaves which could be located at another location than the location of the winches. For example, in many cases, the exit sheaves are located near the centre of gravity of the crane container, so that the wire force is countered by the entire weight of the container. In such cases, the wire tension will not have such a great supporting action on the container. However, in such embodiments, it would be possible to arrange the exit sheaves on a displacement mechanism to allow the exit sheaves to move the point of applied tension on the crane container if it was necessary to support the container in a different way.

[0059] Figure 8 shows another embodiment where two counterweight elements 100 are arranged, one on either end of two pivoting arms 104, said arms arranged one on either side of the crane container 20 (shown in dashed lines). Once the crane container is arranged on the frame element, the pivoting arms could be pivoted 180 degrees so that the counterweight elements are arranged past the tower connection portion 6 (shown in solid lines). This will move the centre of gravity of the combined crane container and counterweight elements from the first location 22’ to the second location 22”. This would provide a good balance and support for the crane container, without the need for very large counterweights which would undesirably increase the shipping weight of the crane container.

[0060] In another embodiment (not shown), it could be imagined that instead of providing a counterweight with a fixed weight in the crane container, a variable weight counter element could be provided. This could for example be provided by a tank arranged in the crane container which can be filled with water. A pump could be arranged to pump water from the water around the water-based platform into the tank. As water is filled into the tank, the centre of gravity of the combined crane container and counterweight element would change. This would be beneficial since it would not be necessary to make the crane container itself much heavier when it is not in use. Only when in use, would the counterweight element need to be activated. Furthermore, by adding more water to the tank or by removing water from the tank, the counterweight could be made more or less heavy, thereby allowing the position of the centre of gravity to be adjusted depending on the need.

[0061] In another embodiment (not shown), the tank could have stretchable walls. In this way, the tank could be small when empty and large when filled with water. In this way, the tank would not occupy much space when transporting the crane container from one location to another, and it would only be necessary to expand the tank once the crane has been lifted out of the crane container. In other embodiments, multiple tanks could be provided in different locations where there is room. Then depending on which centre of gravity position is needed and at which stage in the procedure, one or more of the multiple tanks could be filled with water. In another embodiment, instead of moving a counterweight, one or more of the cranes lifting components could be moved inside the container. For example, the winches could be moved horizontally inside the container towards the tower connection portion. In this way, the centre of gravity of the container would be displaced inwardly.

[0062] Figure 9 shows a foundation element with a concrete base portion 8 and a wind turbine tower mounting portion 6. Furthermore, in this embodiment, a bottom tower section 2 is also partially shown. In this embodiment, the bottom tower section has a bottom flange 120 which is connected to the wind turbine tower mounting portion 6 via a bolt circle 122. The bolt circle comprises a circular array of bolts 124 extending upwardly out of the tower mounting portion 6. Once the tower has been placed on the bolt circle, nuts 126 are screwed onto the bolts to hold the flange of the bottom tower section in place.

[0063] In this embodiment, a support surface 128 is provided and one end 130 of the support surface comprises holes which match the bolts of the bolt circle. The support surface is then engaged with the bolt circle and nuts 126 hold the support surface in place. A compression member 132 is provided between the support surface and the concrete base portion 8 of the foundation element to hold the support surface in a horizontal position. A piece of equipment 134, which could for example be a blade inspection platform, is arranged on the support surface. As can be seen, the equipment is larger than the foundation element and the equipment overlaps the projected area of the foundation element. Furthermore, the centre of gravity 136 of the equipment is arranged outside the periphery (138) of the foundation element. The support surface is therefore necessary to hold the equipment safely on the foundation element.

[0064] The above-described embodiments, have all been described with respect to waterbased platforms which are placed in the water, but close to the shore, such that they can be directly mounded on the bottom surface of the body of water they are arranged in. Such water-based platforms are sometimes called intertidal foundations for wind turbines or intertidal platforms for wind turbines.

[0065] However, the current invention could also be used with platforms which are located far from shore and where there is no firm connection between the bottom surface of the body of water and the foundation element. In some cases, these platforms are located offshore, and as such are called offshore platforms for wind turbines or offshore foundations for wind turbines. Some such platforms are semi submerged platforms where the majority of the platform is arranged under water, while others are floating platforms where the majority of the platform is arranged above the water.

[0066] Figures 10 and 11 disclose a side and top view of an example of a semi-submerged water-based platform 200. The semi submerged platform comprises a foundation element 201 which comprises three vertically arranged cylinders 202a, 202b, 202c connected in a triangular arrangement by horizontal beams 204. The cylinders 202a, 202b, 202c are semi-submerged and are connected to the ocean floor via mooring lines 206 connected to anchors 208. A wind turbine tower 2 is fixed on the platform 200 via a tower mounting portion 6 which is mounted on one of the vertically arranged cylinders 202a. This type of platform is known in the art and it won’t be described in more detail here. A frame construction 210 is provided on one of the vertically arranged cylinders 202b, away from the vertically arranged cylinder 202a which comprises the tower mounting portion 6. A crane container 20 is arranged on the frame construction 210. As before with the other embodiments, a portion of the crane container in this embodiment is arranged outside the projected area of the foundation element. It also extends past the outer periphery of the foundation element. In this embodiment, it should be noted that the frame construction could have been arranged on one of the horizontal bars, between two vertical cylinders 202c, 202b. In this case, a portion of the crane container would have extended out past the outer periphery of the foundation element 210, but a portion of the crane container would also have overlapped the open area 212 between the horizontal beams. This open area would not be considered a portion of the projected area of the foundation element. As such, according to the understanding of the current specification, two portions of the crane container would have been arranged outside the projected area of the foundation element, one on either side of the projected area of the horizontal beam.

[0067] Figures 12 and 13 disclose a side and top view of another example of a semisubmerged platform 300. In this embodiment, the platform comprises a single vertically arranged cylinder 302, extending deeper than the cylinders of the previous embodiment. Again, the cylinder is attached to the seafloor via mooring lines 304 connected to anchors 306. A wind turbine tower 2 is arranged on a wind turbine mounting portion 6 of the cylinder.

[0068] In this embodiment, a frame element 308 with an L shaped structure is provided. The frame element comprises a horizontally arranged support surface 310 and an upwardly extending support portion 312 on the side of the support surface which is closest to the turbine tower. An inner corner edge 314 of the frame element is arranged on an outer portion of the cylinder next to the wind turbine tower. A tension member 316 is connected between the tower mounting portion 6 and the upwardly extending support portion of the frame element. The tension member is a wire wrapped around the tower mounting portion of the cylinder. The tension member applies a moment to the frame element to hold it in place. An additional compression member 318 is provided between the bottom of the support surface 310 and a side portion 320 of the cylinder 302. A schematically shown blade inspection platform 322 is arranged on the support surface.

[0069] Figures 14 and 15 disclose another schematic embodiment of a water-based platform 400 according to the current invention. The platform comprises a foundation element 402 in the form of a floating “barge” with a tower mounting portion 6. A wind turbine tower 2 is arranged on the tower mounting portion. The barge is connected to the sea floor via mooring lines 403 and anchors 404. The barge comprises a rectangular main portion 406 and a U-shaped support portion 408. This type of floating platform is known in the art and won’t be described in more detail here.

[0070] A frame structure 410 is arranged on one corner of the U-shaped support portion. The frame structure supports a horizontally arranged support surface 412. A schematically shown blade repair platform 414 is arranged on the support surface. In this embodiment, an outer portion of the blade repair platform (away from the wind turbine tower) 416 is arranged outside the outer periphery of the foundation element. Furthermore, an inner portion (closer to the wind turbine tower) 418 is arranged inside the outer periphery of the foundation element, but outside the projected area of the foundation element due to the open area 420 inside the foundation element.

[0071] It is to be noted that the figures and the above description have shown the example embodiments in a simple and schematic manner. Many of the specific mechanical details have not been shown since the person skilled in the art should be familiar with these details and they would just unnecessarily complicate this description. For example, the specific materials used and the specific manufacturing procedures have not been described in detail since it is maintained that the person skilled in the art would be able to find suitable materials and suitable processes to manufacture the arrangement according to the current invention.

Claims

Claims1. Water-based platform for a wind turbine, said water-based platform comprising a foundation element which establishes a stable foundation for the wind turbine on the water and a wind turbine tower connection portion arranged on the foundation element, characterized in that said waterbased platform further comprises: a. an equipment support structure and b. equipment for maintaining / servicing the wind turbine, c. said equipment being supported on the foundation element by the equipment support structure, and d. said equipment support structure being connected to the foundation element such that the entire weight of said equipment supported by the equipment support structure is transferred to the foundation element via said equipment support structure.

2. Water-based platform according to claim 1, characterized in that at least a portion of said equipment is arranged outside the projected area of the foundation element when seen from above the foundation element.

3. Water-based platform according to claim 1 or 2, characterized in that said equipment support structure comprises a counterweight element which is arranged in or on said equipment such that the centre of gravity of a combination of said equipment and said counterweight element is closer to the foundation element than the centre of gravity of said equipment alone.

4. Water-based platform according to claim 1 or 2, characterized in that said equipment support structure comprises a counterweight element which is arranged in or on said equipment such that the centre of gravity of a combination of said equipment and said counterweight element is arranged inside the projected area of the foundation element when seen from above.

5. Water-based platform according to any one of claims 1 to 4, characterized in that the equipment support structure comprises a frame element arranged at least partly underneath said equipment to support said equipment.

6. Water-based platform according to claim 5, characterized in that said frame element is detachably attached to the foundation element.

7. Water-based platform according to claim 5 or 6, characterized in that said frame element is arranged to extend from a location on the foundation element to a location away from the foundation element, said location away from the foundation element being further away from the foundation element than a centre of gravity of said equipment.

8. Water-based platform according to any one of claims 5 to 7 characterized in that the equipment support structure comprises detachable fastening elements arranged between said equipment and the frame element.

9. Water-based platform according to any one of claims 1 to 8, characterized in that said equipment support structure comprises a tension member which is attached to the foundation element and to the equipment and / or to an element of said equipment support structure, said tension member being arranged to apply a moment to said equipment and / or to said element to counteract a moment due to the centre of gravity of said equipment.

10. Water-based platform according to any one claims 1 to 9, characterized in that said equipment support structure comprises a compression member which is attached to the foundation element and to the equipment and / or to an element of the equipment support structure, said compression member being arranged to apply a moment to said equipment and / or said element to counteract a moment due to the centre of gravity of the equipment.

11. A water-based platform according to any one of claims 1 to 10, characterized in that said equipment is a crane container and in that said equipment support structure is a crane container support structure.

12. A water-based platform according to claim 11, characterized in that the crane container is a form of container to hold a crane and at least some of its associated lifting equipment.

13. A water-based platform according to claim 12, characterized in that the crane is a self-hoisting crane.

14. A water-based platform according to any one of claims 1 to 13, characterized in that the equipment is arranged such that a centre of gravity of said equipment is arranged outside the projected area of the foundation element when seen from above the foundation element for at least some of the working configurations of said equipment.

15. A water-based platform according to any one of claims 1 to 14, characterized in that the equipment is arranged such that a centre of gravity of said equipment is arranged outside the projected area of the foundation element when seen from above the foundation element for all of the working configurations of said equipment.

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