Foundation for enabling anchoring of a wind turbine tower thereto by means of replaceable through-bolts

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DESCRIPTION

Foundation to allow anchoring of a wind turbine tower to it by means of replaceable through bolts

Technical field

The present invention relates generally to a wind turbine foundation.

In particular, the present invention relates to a foundation to allow the anchoring of a wind turbine tower thereto by means of replaceable through bolts, and to a method of providing such a foundation.

Background of the invention

A wind turbine normally comprises a rotor provided with a set of blades, in which the rotor is arranged on top of a wind turbine tower anchored to a foundation embedded in the ground. Typically, the tower is made of steel, while the foundation is made of reinforced concrete. In order to anchor the steel tower to the concrete foundation, a flange with through holes is provided at the bottom of the steel tower. Anchor bolts, embedded in the concrete foundation and protruding from the surface thereof, can then be driven into the through holes in the flange so that the flange can be fastened with nuts.

An alternative to using bolts embedded in concrete is to use replaceable through bolts that are arranged in through holes in the concrete foundation.

An example of such an arrangement is found in US2007 / 0251187, which discloses a wind turbine foundation with an internal workspace to allow inspection and maintenance of the through bolts and the nuts that fix the bolts. interns to the foundation. The foundation according to document US2007 / 0251187 includes an entrance that provides access to the workspace from inside the tower.

Although it allows inspection of the through bolts, there appears to be room for improvement with respect to the structural strength of the foundation disclosed in US2007 / 0251187. Furthermore, EP 1 849 920 A2 discloses a foundation according to the preamble of claim 1.

Summary of the invention

In view of the above, an object of the invention is to provide an improved wind turbine foundation that can exhibit improved structural strength, allowing a wind turbine tower to be anchored by means of replaceable through bolts.

According to one aspect of the invention, a foundation is provided to allow the anchoring of a wind turbine tower thereto by means of replaceable through bolts, the foundation comprising: a foundation sill with a set of through holes to accommodate the through bolts , wherein the through holes extend from an upper surface to a lower surface of the foundation slab; a workspace disposed below the foundation slab to allow access to lower ends of the through bolts when disposed in the through holes; and a passage that allows access to the workspace from a location outside of an area of ​​the foundation slab to be covered by the tower.

By workspace is known a cavity that is large enough for a worker to access the lower ends of the through bolts.

The present invention is based on the condition that an effective way to improve the structural strength of the foundation is to structurally separate the working space from the foundation slab. The inventor has further found that this can be achieved by providing a passage that allows access to the workspace from a location outside of an area of ​​the foundation slab to be covered by the tower.

In the foundation according to the prior art, a relatively large manhole is provided in the center of the foundation. As a result, the bolts are clamped relatively close to an (inside) edge of the foundation. In order to achieve the structural strength required to allow the anchoring of a wind turbine to be fixed, it is expected that considerable effort will have to be expended in reinforcing the foundation in the vicinity of the through holes.

By instead providing a passage that allows access to the workspace from a location outside the area of ​​the foundation slab to be covered by the tower, the through holes may be arranged in a substantially continuous block of concrete, which may inherently made considerably stronger where it matters most, namely where the through holes are provided. Additionally, the reinforcement configuration can be made simpler, which reduces the time required to build the foundation.

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In addition, less complex formwork can be used when forming the foundation slab, thereby facilitating construction and reducing costs.

The workspace can be defined by at least one prefabricated carcass structure. One advantage is that prefabrication is typically more profitable than on-site production. In addition, the workload at the wind turbine construction site is reduced, thereby shortening the construction time. To facilitate transportation to the wind turbine construction site, the workspace can be provided as two or more prefabricated shell structures and assembled at the wind turbine construction site.

The foundation may also comprise a load distributing element disposed on the bottom surface of the foundation slab to distribute any stresses generated at lower ends of the through bolts over a larger area of ​​the foundation slab. The load distributing element can for example be a steel plate provided with a set of through holes to accommodate the through bolts. The shape of the load distribution element can be for example circular or ring-shaped.

The load distribution element can be an integral part of the at least one prefabricated casing structure, thereby reducing the number of components as well as the workload at the wind turbine construction site. Thus, the load distribution element can be at least partially integrated into the ceiling of the workspace.

The foundation may also comprise a set of hollow tubes extending from the bottom surface to the top surface of the foundation slab thereby defining the through holes in the foundation slab. The tubes, which are configured to accommodate the through bolts, thus separate the through bolts from the concrete in the foundation slab so that the through bolts can be removed from the through holes for example for inspection and / or replacement.

According to an alternative embodiment, each through bolt can be provided with a coating and then embedded in the foundation slab. The coating can thus prevent the concrete from sticking to the through bolt, thereby allowing a replaceable through bolt.

The tubes may optionally be arranged on the load distributing element, such that a bore in each tube coincides with a through hole in the load distributing element (for example by joining the lower end of the tube to the load distributing element ). An advantage is that the pipes are fixed relative to each other, thus reducing the risk of the pipes shifting during embedment in the foundation slab. If the load distribution element is an integral part of the prefabricated carcass structure, the tubes will also be fixed in relation to the workspace.

Also provided is a wind turbine arrangement comprising a foundation according to various embodiments of the present invention; and a wind turbine tower anchored to the foundation by means of replaceable through bolts.

According to another aspect of the invention, a method is provided for providing a foundation to allow the anchoring of a wind turbine tower thereto by means of replaceable through bolts, the method comprising the steps of: providing a foundation slab having a set of through holes for receiving the through bolts, wherein said through holes extend from an upper surface to a lower surface of said foundation slab; provide a workspace below the foundation slab; and providing a passage that allows access to the workspace from a location outside of an area of ​​the foundation slab to be covered by the tower.

This aspect shows similar advantages to the previously discussed aspect of the invention.

The step of providing a workspace may comprise the steps of providing at least one prefabricated carcass structure that defines the workspace. The foundation slab can then be formed on top of the prefabricated carcass structure in situ.

Alternatively, the workspace and / or the passage can be formed by excavation when the foundation slab is in place.

The step of providing a foundation sill may comprise the step of providing a set of hollow tubes defining the through holes; and embed the tubes in the foundation slab. Embedding here means that the outside of the tubes is embedded in the concrete while there is no concrete in the tube bore.

The step of providing a set of hollow tubes may comprise the steps of attaching the tubes to a load distributing element, and arranging the load distributing element above the workspace. According to one embodiment, this can be achieved by arranging the load distribution element to be an integral part of the prefabricated carcass structure.

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A method of anchoring a wind turbine is also provided, comprising the step of anchoring a wind turbine tower to the foundation according to various embodiments of the present invention by means of replaceable through bolts.

Other objects, features and advantages of the present invention will emerge from the following detailed description, from the appended claims as well as from the drawings.

Generally, all terms used in the claims are to be interpreted according to their usual meaning in the technical field, unless explicitly defined otherwise herein. All references to “an / an / the [element, device, component, media, stage, etc.]” ​​should be openly interpreted as referring to at least one instance of said element, device, component, media, stage, etc. ..., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Brief description of the drawings

The foregoing, as well as additional objects, features and advantages of the present invention, will be better understood by the following illustrative and non-limiting detailed description of example embodiments of the present invention, with reference to the accompanying drawings, in which the same numerals reference will be used for similar elements, in which:

Figure 1 schematically illustrates a wind turbine foundation according to a first embodiment of the invention;

Figure 2 is a flow chart schematically illustrating a method for providing a foundation according to one embodiment of the invention;

Figure 3 illustrates a second embodiment of a foundation slab.

Detailed description of the preferred embodiments

Figure 1 schematically illustrates a wind turbine foundation according to a first embodiment of the invention.

Referring to Figure 1, there is a wind turbine 100 comprising a rotor 102 provided with a set of blades 104. The rotor 102 is disposed on top of a tower 106 which is anchored to a foundation sill 116 shown here to be embedded in the ground 112.

The tower 106 is normally made of steel, while the foundation slab 116 is made of reinforced concrete. To anchor the steel tower 106 to the foundation sill 116, a flange 114 with through holes 115 is provided at the bottom of the steel tower. In addition, the foundation sill 116 is provided with a corresponding set of through holes 118. Thus, the tower can be anchored to the foundation slab 116 by arranging the tower on the top surface of the foundation slab 116, aligning the through holes 115 in the flange with the through holes 118 in the foundation slab 116, inserting through bolts. 120 into the aligned holes, and fixing nuts 121a, b at the upper and lower ends of each through bolt (ie for each through bolt a nut 121a is provided on the upper side of flange 115, and a nut 121b is provided on the lower side of foundation sill 116). A load distributing element 122 disposed on a lower surface of the foundation slab distributes the stress generated by the nuts 121b over a larger area of ​​the foundation slab. A workspace 126, which can be accessed via a passage 128, allows a worker to clamp the nut 121b at the lower end of each through bolt 120, as well as subsequently tighten, inspect through bolts and / or, if needed , remove a nut to allow the change of a through bolt.

Furthermore, a cable 136 for transferring power generated by the wind turbine may be arranged in the passage and the workspace. Thus, a small hole (normally having a diameter of about 110mm) is provided in the foundation slab. However, such a small hole will not influence the structural strength of the foundation slab.

Figure 2 is a schematic block diagram of a method for providing a foundation in accordance with a preferred embodiment of the present invention.

A method for providing a foundation according to an embodiment of the present invention will now be described with reference to Figures 1 and 2.

First, in step 201, a workspace 126 is formed in an excavation in the ground. The workspace 126 is here a cavity defined by a carcass structure 126a made of concrete. However, other materials such as for example steel or plastics can also be used.

Although the carcass structure 126a can be fabricated on-site, it may often be preferable to use a structure

ES 2 388 807 T3 with prefabricated housing. In order to facilitate transportation, the workspace can be composed of more than one shell structure and assembled at the wind turbine construction site.

In step 202, a passage 128 is connected to the workspace, to allow a worker to enter the workspace. The passage 128 here is a conventional underground conduit with an associated manhole 130 located proximate the foundation slab 116. A ladder 134 may be provided to facilitate entry and exit.

One of ordinary skill in the art recognizes that the shape and size of passage 128 and workspace 130 may vary depending on the application. However, the passage 128 and workspace 130 must be dimensioned large enough for a worker to enter the workspace 130 and access the lower end of the through bolts 120, for example to allow a nut 121b to be attached, subsequently tensioned, inspect through bolts and / or, if necessary, remove a nut to allow for a through bolt to be changed.

Since most of the force exerted by the wind turbine tower 106 is absorbed by the foundation sill 116, the structural strength requirements are relatively low for the workspace shell structure 126a. However, since concrete is typically poured on top of carcass structure 126a to form the foundation slab, the carcass structure must be able to support the weight of this concrete until the foundation slab has cured. It is recognized that the thickness of the carcass structure can vary (eg due to the design of the carcass structure and the material used therein) and sizing is a matter of course for one of ordinary skill in the art.

At step 203, a load distribution member 122 is provided above the workspace. The load distributing element here is a circular steel plate 122 having a set of through holes 123 configured to accommodate the through bolts. The load distributing element is here an integral part of the workspace shell structure 126 since the steel plate is integrated into the ceiling of the workspace. The load distribution element can also form a complete roof of the carcass structure or a smaller part thereof (for example using a ring-shaped load distribution element). The load distributing element can also be provided separately from the carcass structure.

At step 204, a set of hollow tubes 124 is provided to be embedded in the foundation slab. Here tubes 123 are arranged vertically in load distribution member 122 extending upwardly therefrom. The tubes are arranged such that the perforation of each tube 124 coincides with one of the through holes 123 in the load distributing element. Tubes 124 can be, for example, steel tubes welded to steel plate 122.

However, other materials can also be used for the tubes, such as for example plastic.

Furthermore, the tubes can be attached to a different structure of the load distributing element or provided separately.

In step 205, a foundation slab 116 is formed according to well known techniques for reinforced concrete construction. This can typically include building a formwork that defines the shape of the foundation slab; arranging reinforcing bars therein for improved structural strength of the foundation slab; and pour concrete into the formwork. When concrete is poured into the form, the exterior of the tubes 124 will embed into the concrete (but there will be no concrete inside the tubes).

Since the tubes 124 are fixedly attached to the load distributing member 122, any relative displacement of the tubes is avoided when concrete is poured into the formwork.

In step 206, a base section of a wind turbine tower is arranged on the upper surface of the foundation slab 116. Here, a T-shaped steel flange 114 is provided on the lower part of the base section. . The steel flange 114 has a set of through holes 115, here comprising an inner set of through holes and an outer set of through holes located on the inner and outer side of the tower wall, respectively. The through holes 115 in the steel flange 114 correspond to the through holes 118 in the foundation slab 116. Thus, when the steel flange 114 is disposed on the upper surface of the foundation slab 116, the holes 115 in the steel flange 114 are aligned with corresponding holes 118 in foundation sill 116.

In step 207, a set of through bolts 120 are disposed in the aligned holes and a first nut 121a is attached to the upper end of each through bolt 120 (i.e. above the steel flange 114), and a second nut 121b at the lower end of each through bolt 120 (ie below the load distribution member), thereby anchoring tower 106 to foundation sill 116. Since the load distributing element 122 is disposed between the nuts 121b at the lower ends of the through bolts and the foundation sill 116, the load distributing element 122 distributes the stress generated by the nuts 121b over a larger area. of the foundation slab 116.

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Since the tubes 124 separate the through bolts 120 from the concrete in the foundation sill 116, it is possible to remove the through bolts by loosening the lower nuts.

One skilled in the art recognizes that the shape of the foundation slab can vary. For example, instead of having a flat bottom surface, the foundation slab may enclose the top of the workspace 5 as illustrated in Figure 3.

Above, the invention has been described mainly with reference to a few embodiments. For example, a bolt with a nut on the lower end can be used instead of a through bolt that has nuts on both ends. Furthermore, instead of providing a single plate that works as a load distributing element for all the through bolts in the foundation slab, a plurality of load distributing elements can be used. Although the foundation slab in the illustrated examples is embedded in the ground, alternatively the foundation slab may be partially embedded in the ground or it may be provided above the ground.