Abstract:
A method for operation of a wind energy installation having a rotor ( 18 ) which can be driven by wind and has at least one rotor blade ( 22 ), a generator for conversion of the mechanical energy of the rotor ( 18 ) to electrical energy, a tower ( 14 ) on which the rotor ( 18 ) is arranged, and to guy the wind energy installation ( 10 ) a guy apparatus that is changed as required automatically from an unstressed state which stabilizes the wind energy installation ( 10 ), and a wind energy installation having these features.

Description:
STATEMENT OF RELATED APPLICATIONS 
       [0001]    This patent application is based on and claims priority on German Patent Application No. 10 2006 031 144.2 having a filng date of 4 Jul. 2006. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a method for operation of a wind energy installation having a rotor which can be driven by wind and has at least one rotor blade, having a generator for conversion of the mechanical energy of the rotor to electrical energy, and having a tower on which the rotor is arranged. The present invention also relates to a wind energy installation which is operated using this method. 
         [0004]    2. Prior Art 
         [0005]    Wind energy installations are subject to particularly high loads in strong winds. Wind energy installations are generally designed such that, in the extreme, they can withstand wind speeds which correspond to those of the so-called once-a-century gust. 
         [0006]    However, even in Europe, extreme wind conditions are occurring ever more frequently, with wind speeds which may be above the once-a-century gust. Furthermore, for example in the USA or Australia, there are wind energy installation locations at which it is possible for cyclones or the like to occur. Cyclones can cause wind-dependent forces acting on the wind energy installation which considerably exceed the loads resulting from a once-a-century gust. 
         [0007]    Guys are known for stabilization of buildings in general against external influences, in particular wind. In this case, a plurality of cables, chains or the like which originate from the building to be stabilized are tensioned, and are anchored in the ground. However, the permanent use of guys such as these for wind energy installations would have considerable disadvantages. This is because wind energy installations are subject to dynamic loads. The forces introduced into the wind energy installation as a result of the guys—particularly as a result of the dynamic loads on the wind energy installations—would lead to fatigue problems at those points or in those areas of the wind energy installation into which the forces are introduced. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    One object of the present invention is therefore to specify a method for operation or stabilization of a wind energy installation, by means of which the wind energy installation can be stabilized as optimally as possible, while the corresponding stabilization measures result in as little load as possible on the wind energy installation, at the same time. A further object of the invention is to specify a wind energy installation which can be operated using this method. 
         [0009]    This object is achieved by a method for operation of a wind energy installation having a rotor which can be driven by wind and has at least one rotor blade, having a generator for conversion of the mechanical energy of the rotor to electrical energy, and having a tower on which the rotor is arranged, characterized in that, in order to guy the wind energy installation, a guy apparatus is changed as required automatically from an unstressed state—or at least less-stressed state—to a stressed state—or at least more-stressed state—which stabilizes the wind energy installation. 
         [0010]    Accordingly, according to the invention, in order to guy the wind energy installation, a guy apparatus is changed as required automatically from an unstressed state—or at least less-stressed state—to a stressed state—or at least more-stressed state—which stabilizes the wind energy installation. 
         [0011]    For the sake of simplicity, the following text refers exclusively to a “stressed” or an “unstressed” state. The features of the present invention which are described in the following text in conjunction with these states are intended to relate—without this being expressly mentioned—to the abovementioned change of the guy apparatus from a “less-stressed state” to a “more-stressed state”, as well. 
         [0012]    The particular advantage of the invention is, in particular, that the wind energy installation is guyed only when necessary. The guy apparatus is activated only when stabilization of the wind energy installation is necessary, for example as a result of the current wind conditions. The guy apparatus is unstressed when not activated, so that no guy-dependent forces loading the installation are introduced into the wind energy installation. This effectively reduces fatigue on those components of the wind energy installation which are loaded by the guy. One further particular advantage of the invention is that the guy apparatus is automatically changed from the unstressed state to the stressed state. 
         [0013]    The guy apparatus is preferably changed from the unstressed state to the stressed state as a function of current wind conditions and/or wind conditions to be expected in the future, in particular storm gusts or the like, and/or as a function of current earth movements and/or earth movements to be expected. The guy apparatus is accordingly stressed in order to stabilize the wind energy installation when the wind conditions or other external influences make this necessary. If, by way of example, prediction systems predict storms with such a high wind speed that the wind energy installation could be damaged, the guy apparatus can be stressed. A similar situation exists in the case of currently measured earth (ground) movements or earthquakes or when such events are to be expected, which could cause the wind energy installation to oscillate, so that additional guying could appear worthwhile. 
         [0014]    In one particular embodiment of the present invention, the guy apparatus can be stressed, that is to say it is changed from the unstressed state to the stressed state, once, for example, a critical storm and/or earthquake has been predicted by a specialized institute. In this case, the institute making the prediction can send an activation signal, in particular from an appropriate signal generator, to a control device for the wind energy installation, for example an electromagnetic signal such as a radio signal, a signal which can be transmitted via the Internet, or the like. The control device can then initiate the stressing of the guy apparatus as a function of the activation signal. 
         [0015]    In a further embodiment, it is possible to provide for the wind conditions and/or the ground movements at the location of the wind energy installation and/or in the physical vicinity of the wind energy installation to be recorded by means of suitable sensors, in particular on the side of the wind energy installation facing the wind. However, the wind conditions can also be derived from operating parameters of the wind energy installation, for example from the rotation speed of the rotor, the wind incidence angle of the rotor blade or the like. The guy apparatus can then be changed from the unstressed state to the stressed state as a function of the wind conditions and/or earth movements determined in this way. 
         [0016]    The guy apparatus is preferably changed from the unstressed state to the stressed state when a characteristic value which characterizes the wind conditions and/or the earth movements exceeds a predetermined limit value. 
         [0017]    The guy apparatus is preferably changed back to the unstressed state again when the wind conditions and/or the earth movements allow this. This may be done in particular after a predetermined time period has elapsed and/or as a function of current wind conditions and/or wind conditions to be expected, and/or as a function of current earth movements, and/or earth movements to be expected. When no more loads on the wind energy installation are to be expected or are currently being measured on this basis, the reverse change can be initiated in order to free the wind energy installation of the loads produced by the guying. 
         [0018]    The object of the present invention is also achieved by a wind energy installation having a rotor which can be driven by wind and has at least one rotor blade, having a generator for conversion of the mechanical energy of the rotor to electrical energy, having a tower on which the rotor is arranged, characterized by a guy apparatus which has tensioning means, which can be tensioned controllably and can be changed as required automatically from an unstressed state—or at least from a less-stressed state—to a stressed state—or at least to a more-stressed state—which stabilizes the wind energy installation. 
         [0019]    Accordingly, a wind energy installation which is being operated using the method as described above has a guy apparatus which has tensioning means, which can be tensioned controllably and can be changed as required automatically from an unstressed state or to a stressed state which stabilizes the wind energy installation. 
         [0020]    The tensioning means may, for example, be cables, chains or the like which are connected at one end to the tower of the wind energy installation and/or to the nacelle. The tensioning means are preferably anchored or can be anchored, at the other end directly or indirectly in the ground. In this embodiment, the tensioning means run obliquely downward, starting from the wind energy installation, to the respective anchorage points in the ground, which are arranged around the wind energy installation. 
         [0021]    The guy apparatus can be controlled by means of an open-loop/closed-loop control device as a function of the wind conditions and/or earth movements which are currently being recorded and/or are to be expected in the future. The tensioning means are accordingly stressed when this is necessary as a result of the wind conditions and/or the earth movements. 
         [0022]    For automatic stressing of the tensioning means, the guy apparatus can have a motor, in particular electric-motor, hydraulic or pneumatic drive, via which the tensioning means can be stressed. 
         [0023]    In one particularly preferred embodiment of the present invention, the rotor of the wind energy installation is braked before the guy apparatus is changed from the unstressed state to the stressed state, in particular by suitable variation of the wind incidence angle on the rotor blades and/or by operation of mechanical rotor brakes. Since the rotor blades are braked before the guy apparatus is stressed, the tensioning means of the guy apparatus can be stressed without impediment without any need to be concerned about collisions between the tensioning means and the rotor blades as a result of the rotation of the rotor blades. The tensioning means, for example the cables, can then be attached to the tower of the wind energy installation for example particularly high up, without the cables, which run obliquely downwards from the tower in the stressed state, being hit by the rotating rotor blades. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Further features of the present invention are specified in the attached dependent claims, in the following description of one preferred exemplary embodiment, and in the attached drawing, in which: 
           [0025]      FIG. 1  shows a schematic side view of a wind energy installation according to the invention with a guy apparatus. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0026]      FIG. 1  shows a wind energy installation  10 . The wind energy installation  10  has a nacelle  16 , which is arranged at the top of the tower, at the upper end of a vertical tower  14  which is arranged on a horizontal base  12 . As a person skilled in the art knows from the prior art, many embodiments are feasible for the detailed design of a tower  14  for a wind energy installation  10 . The invention is not, of course, restricted to the truncated-conical form of the tower  14  described in the drawing. 
         [0027]    A rotor  18  is arranged at an end of the nacelle  16  facing the wind, and has a hub  20 . Three rotor blades  22  are connected to the hub  20 , with the rotor blade roots  23  of the rotor blades  22  being inserted into appropriate openings in the hub  20 , and being connected to it in a known manner. 
         [0028]    The rotor  18  rotates about an axis which is inclined slightly upward with respect to the horizontal. As soon as wind strikes the rotor blades  22 , the rotor  18  is caused to rotate about the rotation axis, together with the rotor blades  22 . The movement of the rotor shaft is converted to electrical power by a generator which is arranged within the nacelle  16 . The rotor blades  22  cover a circular area during rotation. The positions of the rotor blades  22  with respect to the wind can be varied individually by means of an adjustment device, which is not illustrated but is known to those skilled in the art from the prior art, that is to say the incidence angle of the rotor blade  22  with respect to the wind is adjustable. Various functions of the wind energy installation  10  can be controlled by a suitable control device, which is not illustrated. 
         [0029]    The wind energy installation  10  is connected to an electricity grid system, into which the electrical energy produced by the generator can be fed. 
         [0030]    The basic design of the wind energy installation  10  with an at least approximately horizontal rotor axis is known from the prior art, so that this will not be described in detail. 
         [0031]    The tower  14  of the wind energy installation  10  is guyed by means of a guy apparatus  24 , that is to say it is stabilized with respect to external influences, such as wind gusts or earth movements, in particular relatively minor earthquakes. The guy apparatus  24  has three upper tensioning means  28  as well as three lower tensioning means  26 , which each end at the tower  14  of the wind energy installation  10 . Only four tensioning means of the tensioning means  26 ,  28  can in this case be seen in the present side view. All of the tensioning means  26 ,  28  are in the form of cables. 
         [0032]    The upper tensioning means  28  are connected to the tower  14  in its upper third. Starting from the attachment points  29 , they run obliquely downwards and end in the immediate vicinity of the tower  14  at anchoring devices  30  for the guy apparatus  24 . 
         [0033]    The anchoring devices  30  are anchored in the ground  12  by means of anchoring foundations, which are not shown. 
         [0034]    The lower tensioning means  26  are connected to the tower  14  in its lower half. Starting from attachment points  32 , they likewise run obliquely downwards to the anchoring devices  30  for the guy apparatus  24 . 
         [0035]    The anchoring devices  30  for the guy apparatus  24  have drives, specifically electric motors, via which the tensioning means  26 ,  28  can be changed by means of cable winches, which are not illustrated, from an unstressed state, which is not illustrated, to the stressed state as shown in  FIG. 1 . For this purpose, the tensioning means  26 ,  28  are each wound up in a manner known per se by means of the cable winches onto appropriate cable winch drums. In order to change the tensioning means  26 ,  28  back to the unstressed state, the tensioning means  26 ,  28  can be unwound from the cable winch drum. In the unstressed state, the tensioning means  26 ,  28 , that is to say the cables, hang down loosely adjacent to the tower  14  in places, and lie on the ground  12  in places. 
         [0036]    The guy apparatus  24  can be controlled by means of an open-loop/closed-loop control device, which is associated with the wind energy installation  10 , as a function of the currently recorded wind conditions and/or earth movements and/or similar events to be expected in the future. The tensioning means  26 ,  28  are automatically stressed in a corresponding manner when this is necessary as a result of the wind conditions and/or the earth movements. 
         [0037]    Specifically, the guy apparatus  24  is changed from the unstressed state to the stressed state as a function of an activation signal which is transmitted to the open-loop/closed-loop control device directly or indirectly from an institute predicting wind and/or earth movements. 
         [0038]    Alternatively or additionally it is feasible for the wind conditions and/or the earth movements at the location of the wind energy installation  10  and/or in the physical vicinity of the wind energy installation  10  to be recorded by means of suitable sensors, in particular on the side of the wind energy installation  10  facing the wind. The wind conditions can also be derived from operating parameters of the wind energy installation  10 , for example from the rotation speed of the rotor  18 , from the wind incidence angle of the rotor blade  22 , or the like. 
         [0039]    The guy apparatus  24  is changed back to the unstressed state after a predetermined time period has elapsed and/or as a function of current wind conditions and/or as a function of current earth movements. 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
           10  Wind energy installation 
           12  Base 
           14  Tower 
           16  Nacelle 
           18  Rotor 
           20  Hub 
           22  Rotor blades 
           23  Rotor blade root 
           24  Guy apparatus 
           26  Lower tensioning means 
           28  Upper tensioning means 
           29  Attachment points 
           30  Anchoring device 
           32  Attachment points