Abstract:
An arrangement comprising a tower of a wind turbine and a damping device, wherein the tower is situated on a surface. Notably, the damping device is arranged between the tower and the surface. The surface may also been described as the ground or as a floor where the tower is situated on or located at.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to European application No. EP16179946.5, having a filing date of Jul. 18, 2016, the entire contents of which are hereby incorporated by reference. 
       FIELD OF TECHNOLOGY 
       [0002]    The following relates to an arrangement comprising a tower of a wind turbine and a damping device, wherein the damping device is arranged and prepared to reduce undesired movements of the tower. In particular, the inventive arrangement relates to undesired oscillatory movements of the tower. 
       BACKGROUND 
       [0003]    A common problem of wind turbine towers are undesired movements of the tower, wherein these undesired movements often times having the characteristics of oscillatory movements. These undesired tower movements mainly occur because a tower of a wind turbine is typically an elongated object having a considerable length. Therefore, the wind turbine tower is exposed to wind which impinges on the wind turbine tower and cause these movements. Oscillation of the wind turbine towers mainly occur during storage of the tower at a storage site, often close to a harbor, or during transportation of the tower on a vessel to an offshore installation site of the wind turbine. 
         [0004]    Until now, these undesired tower oscillations have widely been accepted. They are, for instance, encountered by reinforced attachment devices of the tower with regard to the ground where the tower is situated on. 
         [0005]    An alternative method to cope with the problem of these undesired movements of the tower are the provision of VIV (vortex induced vibration) strakes which are attached to the tower. Preferred sections of the tower where the VIV strakes are mounted on are the upper third or upper half of the tower. 
         [0006]    The drawbacks of the approach to include VIV strakes are safety issues during mounting and dismounting of the VIV strakes to and from the tower, respectively, and the risk that the coating, i.e. paint, of the tower is damaged by the VIV strakes. 
         [0007]    In more detail, the safety issue during mounting of the VIV strakes consists of the fact that someone needs to climb up the tower for working on the top platform of the tower, which means that work at a considerable height, for example higher than 100 meter above ground, needs to be carried out. The same problem occurs during dismounting of the VIV strakes. Additionally, additional costs due to the labor work exist. There is also the drawback that are part of strakes are dropped off and hit the ground. 
         [0008]    With regard to the damage to the paint, repairing these damages in particular off-shore is very expensive. 
         [0009]    Bearing all these drawbacks of the state of the art in mind, an improved concept of reducing movements, in particular oscillatory movements, of the tower of the wind turbine with regard to the ground where the tower is situated on, is desired. 
       SUMMARY 
       [0010]    An aspect relates to providing an arrangement comprising a tower of a wind turbine and a damping device, wherein the tower is situated on a surface, and wherein the damping device is arranged between the tower and the surface. 
         [0011]    Note that embodiments of the present invention are not directed towards a damping device inside or outside of the tower which aims to prevent undesired movements of the tower during operation of the wind turbine. Moreover, embodiments of the present invention propose the provision of a damping device between the tower of the wind turbine and the surface. The surface may also been described as the ground or as a floor where the tower is situated on or located at. 
         [0012]    The ground may be part of a deck of a vessel and the tower may be temporarily located on the deck of the vessel. This application of the inventive concept is therefore directed to off-shore wind turbines, i.e. towers of a wind turbine which are used for off-shore installations of wind turbines. The notion “temporarily” includes time spans of a day, several days or weeks but not exceeding a maximum time span of two months. 
         [0013]    Another possible situation wherein embodiments of the present invention are useful is the scenario where the tower is situated on or at a storage site ashore and the tower is temporarily located at the storage side ashore, e.g. close to or at a harbor. 
         [0014]    Typically, before transportation of the wind turbine tower to the installation site ashore, the tower is stored at a certain area. This area is advantageously located close to the harbor or even is a part of the harbor. During the time at which the tower is actually transported on the vessel to the installation site, the tower is also exposed to wind and therefore may also suffer from undesired movements, for example oscillatory movements. Therefore, it is also desired to reduce and minimize these movements. By providing a damping device between the tower and the surface during this time, a benefit is also reached. 
         [0015]    Note that the notion “temporarily” in this context amounts to typically a few days, weeks or a few months. For the temporary storage of the tower at the storage site, extended time spans may apply meaning several months. However, a time span of two years maximum is not exceeded. 
         [0016]    Yet, another use or application of embodiments of the present invention is the provision of the damping device between the tower and the surface while the tower is permanently attached to a foundation. Therefore, in this context, the notion “surface” has to be understood as being a part of the foundation of the wind turbine. 
         [0017]    A tower is called and understood to be permanently attached if the attachment is present during a time span exceeding two years. In other words, it may also be advantageous to use embodiments of the present invention for a permanent installation of the wind turbine as therefore undesired movements of the tower are permanently minimized. 
         [0018]    The tower may be understood as an elongated object with a longitudinal axis. The longitudinal axis of the tower may advantageously be orientated substantially vertical with regard to the surface. 
         [0019]    In particular, the tower of the wind turbine is standing on the surface. The present inventive concept is particularly beneficial if the tower is erected and has a substantially vertical orientation. 
         [0020]    “Substantial” in this context refers and includes deviations up to 20%, in particular 10% of a perfect vertical orientation. 
         [0021]    Note, however, that in principal the concept may also be applied to towers which are arranged in a different orientation, for example an angled orientation comprising an angle smaller than 90 degrees. In principle, the concept may even be applied to horizontally stored towers. 
         [0022]    In a particularly beneficial embodiment of the invention, the damping device comprises a laminated elastomeric bearing comprising an inner elastomeric material, in particular rubber, a first connector plate and a second connector plate. The laminated elastomeric bearing is arranged between the two connector plates, wherein the first connector plate is arranged and prepared to be connected to the surface, and the second connector plate is arranged and prepared to be connected to the tower. 
         [0023]    The configuration of the damping device, in particular the configuration of the laminated elastomeric bearing being arranged between the two connector plates, may also be described as a sandwich configuration. Such a configuration has been proven to be particularly efficient both with regard to the damping potential and with regard to the ability to tightly and reliably connect the damping device to both the surface and the tower. 
         [0024]    In another embodiment of the invention, the damping device furthermore comprises a supporting element, such as an annular frame or a plurality of individual supporting blocks. The first connector plate is connected to the surface via the supporting element. 
         [0025]    In other words, in this embodiment of the invention, the damping device is not connected directly to the surface, but a supporting element between the damping device and the ground is included. In other words, the supporting elements such as a frame or individual supporting blocks are a part of the damping device. 
         [0026]    In another embodiment of the invention, the tower comprises a base flange, and the second connector plate is connected to the base flange of the tower. 
         [0027]    It is common that a tower of a wind turbine comprises a flange at its bottom end. Via this flange the tower is usually connected to the foundation, i.e. to the surface. Therefore, beneficially, the second connector plate of the damping device is connected to the tower at the bottom end, in particular at the base flange of the tower. 
         [0028]    In another embodiment of the invention, the damping device furthermore comprises an adaptor plate, and the second connector plate is connected to the base flange of the tower via the adaptor plate. 
         [0029]    An advantage of the provision of such an adaptor plate is a facilitated and more efficient actual connection between the second connector plate to the base flange of the tower. Such an adaptor plate may be designed and customized according to the specific specification of the base flange of the tower without the need of adapting the second connector plate of the damping device. Therefore, a more standard setup of the damping device, in particular the second connector plate of the damping device, is possible. 
         [0030]    In yet another embodiment of the invention, the adaptor plate is attached to the base flange of the tower by a plurality of bolts. Such a bolt connection of the adaptor plate to the base flange has the advantage that it can easily be carried out when the damping device is connected to the tower of the wind turbine and that such a connection is detachable. In particular, for the case of a temporary use of the damping device, an easy and efficient detachment of the damping device from the tower of the wind turbine is important. 
     
    
     
       BRIEF DESCRIPTION 
         [0031]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0032]      FIG. 1  shows an arrangement comprising a tower of a wind turbine and a damping device; 
           [0033]      FIG. 2  shows an arrangement comprising a tower of a wind turbine in a damping device in a cross sectional view; 
           [0034]      FIG. 3  is a close-up view of a base flange of the tower being connected to a damping device; 
           [0035]      FIG. 4  shows a damping device including several individual supporting blocks; and 
           [0036]      FIG. 5  shows an explosion view of an embodiment of a damping device. 
       
    
    
       [0037]    The illustration in the drawings is schematically. Note that similar features and elements are denoted by the same reference signs accordingly. 
       DETAILED DESCRIPTION 
       [0038]      FIG. 1  shows an arrangement comprising a tower  10  of a wind turbine, which is arranged upon a damping device  20 . The tower  10  has a tubular shape and is slightly tapered towards the top of the tower. The tower  10  is sitting at its bottom on the damping device  20 . The damping device  20  is illustrated in more detail in the following drawings. 
         [0039]    A cross sectional view of the inventive arrangement is illustrated in  FIG. 2 . Therein, a part of a tower  10  of a wind turbine can be seen. The tower  10  has a rotationally symmetric shape such that a longitudinal axis  11  can be assigned to the tower  10 . The angle between the longitudinal axes of the tower  11  and the surface  30  is 90 degree. In other words, the tower  10  is vertically directed on the surface  30 . However, the tower  10  is not located directly on the surface  30 , but a damping device  20  is arranged between the bottom of the tower  10  and the surface. The damping device  20  comprises several individual elements. Each individual element comprises a laminated elastomeric bearing  21 , which is sandwiched between a first connector plate  22  and a second connector plate  23 . The first connector plate  22  is arranged towards the tower  10 . However, there is provided an adaptor plate  24  between the tower  10  and the first connector plate  22 . This adaptor plate  24  facilitates the connection between the first connector plate  22  and the bottom end of the tower  10 . 
         [0040]    The second connector plate  23  is also not directly connected to the surface  30 . However there is also for seen a further element which is referred to as a supporting block  25  between the second connector plate  23  and the ground  30 . This supporting block  30  is one of several possibilities of a supporting element in general. Alternatively, instead of providing a plurality of individual supporting blocks, there may for example also be provided a circular frame for supporting the remaining parts of the damping device. 
         [0041]      FIG. 3  shows a close-up view of the arrangement comprising a tower  10  of a wind turbine and a damping device  20 . The tower  10  is shown as comprising a base flange  12  and tower walls which in  FIG. 3  are only for sake of clarity drawn as dash-dotted lines. In practice, the tower walls and the base flange  12  may well be manufactured as one piece and the base flange  12 , in particular its inner ring, may well be invisible from the outside. 
         [0042]    The base flange  12  of the tower  10  is connected to the damping device  20  via a plurality of base flange bolts  28 . In the example as illustrated in  FIG. 3 , five base flange bolts  28  are used for each individual supporting block  25 . Note that of course the base flange bolts  28  do not extend through until the supporting blocks  25  but just connect the base flange  12  with the adaptor plate  24 . 
         [0043]      FIG. 3  furthermore discloses the first connector plate  22 , the laminated elastomeric bearing  21  and the second connector plate  23 .  FIG. 3  also shows the bolts  26  which connect the adaptor plate  24  with the first connector plate  22 . 
         [0044]      FIG. 4  only shows the damping device  20  without illustrating the tower of a wind turbine. Again, the damping device  20  comprises a plurality of supporting blocks  25  which are directly connected to the first connector plate  22 . The first connector plate  22  is connected to the laminated elastomeric bearing  21  which is sandwiched by the second connector plate  23  on the other side. The second connector plate  23  is connected via bolts  26  with an adaptor plate  24 . 
         [0045]    Finally,  FIG. 5  illustrates in an explosion view an embodiment of an inventive damping device. It can be well seen that the damping device comprises as a key element laminated elastomeric bearing  21  which are covered at the top and at the bottom by the first connector plate  22  and the second connector plate  23 , respectively. The second connector plate  23  is connected via a plurality of bolts  26  with an adaptor plate  24 . Also note the five base flange bores  27  which are drilled into the adaptor plate  24 . These base flange bores  27  are arranged and prepared to accommodate and receive the base flange bolts  28 , which are for example disclosed in  FIG. 3 . 
         [0046]    Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. 
         [0047]    For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.