Patent Publication Number: US-2021163268-A1

Title: A method of handling a wind turbine component and a wind turbine with a crane

Description:
FIELD OF THE INVENTION 
     The disclosure relates to a method of handling a wind turbine component in a wind turbine. Particularly, the method relates to a wind turbine comprising a tower extending in an upwards direction, a load carrying structure extending in an outwards direction and being fixed to the tower, and an energy generating unit fixed to the load carrying structure. Such structures are typically seen in multiple rotor wind turbines. In such wind turbines, the outwards direction is transverse to the upwards direction. 
     The invention further relates to a lifting system and a crane for handling wind turbine components. 
     BACKGROUND OF THE INVENTION 
     In wind turbines, wind energy is converted into mechanical energy by blades carried by a hub. The hub may be carried by a shaft. The size and weight of the wind turbine tower, nacelle, blades, and drive train have increased over the years and manufacturing, transport, and assembly of the wind turbines have become more and more challenging. 
     Modern wind turbines may include towers which are more than 100 meters tall. 
     In multirotor wind turbines the energy generating units may be carried by a load carrying structure which, in turn, is connected to a tower. 
     A conventional approach for assembly of wind turbines, and particularly the nacelle, includes lifting the components by use of an external crane, e.g. a mobile crane or a floating crane. 
     Since external crane operations are expensive, the nacelle is sometimes fitted with an internal crane which, once the nacelle is installed, can be used for servicing and minor repair, e.g. for hoisting spare parts from the ground into the nacelle. However, for cost optimization, such integrated cranes are normally small and lacks the capacity to handle large or heavy wind turbine components. 
     DESCRIPTION OF THE INVENTION 
     It is an object of the present disclosure to reduce costs in handling wind turbine components, and particularly to facilitate the assembly of wind turbines. 
     According to these and other objects, the disclosure, in a first aspect, provides a method of handling a wind turbine component in a multiple rotor wind turbine, the method comprising:
         providing a crane with a fixation structure configured for fixing the crane to an attachment point on the load carrying structure or on to the energy generating unit,   using a lifting rope attached to the load carrying structure or to the energy generating unit for hoisting the crane to the attachment point,   attaching the fixation structure of the crane to the attachment point, and   using the crane to handle the wind turbine component.       

     In a second aspect, the disclosure provides a wind turbine with a crane. 
     Due to the crane, time and money can be saved during the installation of the wind turbine. Particularly, the use of a lifting rope for mounting the crane to the attachment point enables the use of the crane for mounting e.g. the energy generating unit and other large components. This enables assembly of the wind turbine without the use of external cranes. 
     The method may e.g. be applied for mounting a component when erecting the wind turbine or for dismounting or replacing a component during repair or servicing. The mounting or dismounting may include positioning or dispositioning for removing the wind turbine component completely or in parts. The component could e.g. be a part of a drive train, e.g. a rotor shaft, a gear box, a generator, a hub, or a blade for the hub. 
     In the present context, the term ‘multirotor wind turbine’ should be interpreted to mean a wind turbine comprising two or more rotors or energy generating units mounted on one tower. The load carrying structure is arranged for supporting at least one of the at least two energy generating units and for being connected to a tower of the multirotor wind turbine. 
     The load carrying structure may be configured for self supporting carrying of the energy generating unit, or it may be configured for being further stiffened or stabilised by additional structures such as tension elements such as guy wires etc. One or more guy wires could be attached during use of the crane, and in one embodiment, they could be removed when the crane is removed or they are left on the wind turbine to support the load carrying structure even when the crane is removed. 
     Accordingly, the load carrying structure forms a connection between the one or more energy generating units and the tower, and is capable of handling the loads involved with carrying the at least one energy generating unit. Particularly, the load carrying structure may be constituted by a first component and a second component, the components being structurally different. The first component may e.g. be a lightweight component, e.g. a hollow component, a lattice structure or similar relatively light weight structure constituting the largest part of the load carrying structure. The first component may e.g. be a tube. The second component may be arranged as a termination of the first component at the free end furthest away from the tower. The second component could be relatively heavy compared to the first component, and it may e.g. be constituted by a casted component. Particularly, the second component may have a higher rigidity, strength, or hardness than the first component. The second component may be referred to as the ‘bell’. 
     The energy generating unit is typically arranged at or near the end of the load carrying structure. By the abovementioned first and second components constituting the load carrying structure, the energy generating unit may particularly be fixed to the second component, the bell, either directly or via an adapter. 
     Typically, two load carrying structures are arranged on opposite sides of the tower to thereby balance forces and loads with respect to the tower. The energy generating units may be arranged at extremities of the load carrying structures, i.e. furthest away from the tower. 
     The load carrying structure may be attached to the tower via a yaw arrangement whereby the load carrying structure is allowed to perform yawing movements with respect to the tower, thereby allowing the rotors of the energy generating units to be directed into the incoming wind. 
     In the present context the term ‘energy generating unit’ should be interpreted to mean a part of the wind turbine which transforms the energy of the wind into electrical energy. Normally, this constitutes a nacelle and a rotor. 
     In the present context the term ‘tower’ should be interpreted to mean a substantially vertical structure, arranged to carry the energy generating units of the multirotor wind turbine, at least partly via one or more load carrying structures. One or more energy generating units could be mounted directly on the tower. 
     The load carrying structure may particularly be constituted by a compression element which is carried by a tension element. The compression element may e.g. be a rigid tubular steel element or a steel element with any alternative shape making it suitable for compensation of compressive forces. The tension element could be a rod or wire forming a guy wire extending between the tower and the load carrying structure. As mentioned above, the compression element may comprise a first and a second component. 
     The outwards direction of the load carrying structure could be perpendicular to the upwards direction of the tower, or it could be a direction in the range of 5-25 degrees, such as 15 degrees upwards relative to perpendicular, i.e. pointing upwards. 
     The crane could be released from the attachment point and removed from the wind turbine once handling of the wind turbine component is ended. 
     When used herein, the term ‘crane’ could be a machine of any kind and equipped with means enabling its use for hoisting and/or lowering the wind turbine component. Such means may include e.g. a jack-up arrangement and/or a crane rope powered by a lifting power structure, e.g. an electric or hydraulic winch. When used herein, the term ‘crane’ is the crane which according to the invention is lifted to the load carrying structure by the lifting rope. Other cranes are mentioned with a prefix, e.g. ‘internal crane’, ‘external crane’ etc., but the word ‘crane’ without a prefix denotes the crane lifted with the lifting rope. 
     In one embodiment, the lifting rope is the crane rope and can be winded in or out by the lifting power structure. In this embodiment, the crane rope which constitutes the lifting rope could be attached to an internal hoisting rope of an internal or interim crane, e.g. an internal crane which is small relative to the crane. Herein, an interim crane is a small crane attached only for the purpose of lifting the crane to the load carrying structure. The interim crane thus constitutes an internal crane once it is attached. 
     By use of the smaller internal crane and the internal lifting rope, the lifting rope could be lifted to the load carrying structure or to the energy generating unit by use of the internal crane. Subsequently, the lifting rope is fixed to the load carrying structure or to the energy generating unit and the crane could be lifted by the lifting rope and by use of the lifting power structure included in the crane, i.e. the crane may lift itself. 
     The crane may particularly be attached to an attachment point at or near the end of the load carrying structure. By the aforementioned first and second components constituting the load carrying structure, the attachment point may particularly be a point on the second component, i.e. the bell. 
     The term ‘rope’ should herein be interpreted as any kind of flexible tension member, e.g. in the form of a wire, a chain, or similar element. Typically, the crane includes a sheave around which the crane rope is winded and which forms a point of release for the crane rope. 
     The lifting rope is attached to the crane and used for lifting the crane from ground or sea level to the load carrying structure. The lifting rope could be any kind of flexible tension member, e.g. in the form of a wire, a chain, or similar element. 
     The lifting rope could be attached to the fixation structure, i.e. to that part of the crane which is fixed to the attachment point. Particularly, the lifting rope may be attached between the load carrying structure and the fixation structure such that the fixation structure can be lifted directly into a position which is suitable for fixing the crane to the load carrying structure. The lifting rope may also be constituted by the crane rope. 
     The fixation structure may e.g. be configured to interface the load carrying structure in a predetermined orientation, and the crane could be provided with a weight distribution such that it can be lifted with the lifting rope attached to the fixation structure and be in balance in an orientation, herein referred to as ‘balance orientation’, which matches the predetermined orientation. Herein ‘matches’ means that the crane, when lifted in the fixation structure, maintains an orientation in which the fixation structure can engage and be fixed to the attachment point. 
     The fixation structure and the attachment point may particularly facilitate geometric locking of the crane to the load carrying structure or energy generating unit. As an example, the fixation structure may include one or more projections cooperative with one or more indentations or holes on the load carrying structure, or the fixation structure may include one or more indentations or holes cooperative with one or more projections on the load carrying structure. Particularly, such projections, or indentations, or holes, could have a cross section suitable for guiding the crane into a correct position on the load carrying structure, e.g. a pyramid or conic shape of projections of the fixation structure or on the load carrying structure. Further, such projections, or indentations, or holes, could have a cross section suitable for preventing reorientation of the crane relative to the load carrying structure, e.g. a non-circular cross section. 
     The crane may be configured to form contact with the load carrying structure below a geometric centre of a cross section of the load carrying structure transverse to the outwards direction. Further the crane may be provided such that it extends in contact with the load carrying structure from the point below the geometric centre to a point above the geometric centre. In one embodiment, the fixation structure forms a U-shaped, a C-shaped, a horse-shoe-shaped, or a similar shaped structure which can clamp around the load carrying structure from a point below its geometric centre to a point above its geometric centre. 
     The crane could be provided with a hoisting point, e.g. a sheave, forming a point of suspension of the crane rope, and it could be provided such that the position of the hoisting point is movable relative to the position of the fixation structure. In one example, the crane comprises one or more elements movable relative to each other, e.g. elements linked in hinges and movable by power driven means. 
     The load carrying structure could be supported by a tension element in the form of a guy wire extending from the tower to a support point on the load carrying structure. The support point may typically be arranged at or near the end of the load carrying structure. By the aforementioned first and second components constituting the load carrying structure, the support point may particularly be a point on the second component, i.e. the bell. 
     In that way, the crane can be attached in the area where the load carrying structure is supported and the ability to handle heavy wind turbine components by use of the crane is increased while the guy wire prevents deflection of the load carrying structure. 
     A tagline could be connected to the crane when the crane is lifted by the lifting rope. In that way, the crane could be guided past obstacles during the hoisting procedure, e.g. if the wind turbine comprises more than one load carrying structure and the crane has to be lifted past a lower one of the load carrying structures for fixation to an upper one of the load carrying structures. 
     Once the crane is fixed to the attachment point, the method may be applied for lifting extension components suitable for extending the crane structure. I.e. the crane can be expanded in size or lifting capability by lifting extension components to the crane by use of the crane. In that way, the method may imply the step of, initially, lifting a relatively small or light weight crane and subsequently expanding the crane by lifting extension components. 
     Additionally, the method may include the use of the crane for lifting a further crane and fixing the further crane to the load carrying structure. Subsequently, the crane and the further crane may cooperate in handling the wind turbine component. 
     The crane could be hoisted in one single hoisting procedure and in one single piece after complete assembly of the crane at a factory or at the place where the wind turbine is assembled. Alternatively, the crane could be hoisted in several separate pieces in several subsequent hoisting procedures, and assembled on or at the load carrying structure. In one example, the fixation structure is hoisted firstly and attached to the attachment point, and further components are hoisted subsequently and attached to the fixation structure. 
     In a second aspect, the disclosure provides a wind turbine comprising a tower extending in an upwards direction, a load carrying structure extending in an outwards direction and being fixed to the tower, and an energy generating unit fixed to the load carrying structure, wherein the outwards direction is transverse to the upwards direction, the wind turbine further comprising a crane attached to an attachment point of the load carrying structure or on the energy generating unit. 
     The load carrying structure may comprise at least a first component and a second component, and the second component may form an axial termination of the first component and have a higher strength than the first component. In this embodiment, the attachment point may be a point on the second component. Further, in this embodiment, the second component could be a casted component. The second component may form a connection interface to the first component and an interface to the energy generating unit. 
     The wind turbine may comprise a tension element, e.g. a guy wire, extending between the tower and a support point on the second component. 
     In further aspects, the disclosure may provide a crane with crane rope powered by a lifting power structure which is sufficiently strong to allow the crane to lift itself. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in further detail with reference to the accompanying drawings in which 
         FIG. 1  illustrates a front view of a multiple rotor wind turbine, 
         FIG. 2  illustrates a crane for handling wind turbine components, 
         FIG. 3  illustrates a load carrying structure, 
         FIG. 4  illustrates a lifting rope attached to the crane and used for lifting the crane to the attachment point, 
         FIG. 5  illustrates a wind turbine with an attached crane, 
         FIG. 6  illustrates an attached and unfolded crane, 
         FIG. 7  illustrates a crane with internal power means for lifting the crane, 
         FIGS. 8 and 9  illustrate the crane attached and unfolded, 
         FIG. 10  illustrates details of the load carrying structure and a guy wire for supporting the structure, and 
         FIGS. 11-31  illustrate mounting of the crane in a specific example by use of an interim crane. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a front view of a multirotor wind turbine  101  comprising a tower  102  carrying four load carrying structures  103 . The load carrying structures  103  are arranged, in pairs of two, one pair above the other. 
     The load carrying structures in a pair of load carrying structures extend in opposite outwards directions away from the tower  102 . 
     Each load carrying structure  103  supports an energy generating unit  105 , and each energy generating unit  105  comprises a nacelle  106  and a rotor  107  carrying three wind turbine blades  108 . Each energy generating unit  105  is connected to a load carrying structure via a rotational joint. 
     The load carrying structures  103  are attached to the tower  102  via a yaw arrangement  111 , allowing the entire pair of load carrying structures to perform yawing movements with respect to the tower  102  in order to direct the rotors  107  into the incoming wind. 
     When the multirotor wind turbine  101  is operational, the energy generating units  105  are placed symmetrically around the tower  102  so that the multirotor wind turbine is balanced. 
     For maintenance and service, components  112  can be hoisted from ground to the nacelle by an internal hoisting rope  113  of an internal crane in the nacelle. The internal crane has very limited lifting capability. 
     The wind turbine comprises guy wires  114  attached either momentary for the purpose of supporting the load carrying structure while the crane is used or stationary, i.e. also after the crane is removed. 
       FIG. 2  illustrates a crane  21  which is configured for facilitating improved handling of components  112  in wind turbines. The crane is configured for being lifted to an attachment point and for releasable fixation to a wind turbine. The crane  21  comprises a fixation structure  22  configured for fixing the crane to the attachment point and a hoisting point  23  formed with a sheave  24  which guides a crane rope  25  and which can be used for lifting the wind turbine component to be handled. Between the fixation structure and the hoisting point, the crane forms a crane body. The crane body may particularly be a lightweight construction, e.g. a frame construction made of lightweight steel bars etc. 
     The crane body includes a hinge structure  26  which allows rotation of a first body part  27  relative to a second body part  28  and thus enables movement of the hoisting point  23  relative to the fixation structure  22 . 
     In a front end of the second body part, the crane forms the illustrated hoisting point  23 , in an opposite, second, end of the second body part, the crane forms a combined counterweight and control unit  29 . The counterweight provides balance relative to the hinge structure  26  and thereby allows lifting of heavy components, and the control structure may include power driven means for driving the crane rope  25 . 
       FIG. 3  illustrates a load carrying structure comprising a first part  31  and a second part  32 . The first part is a hollow tubular element, and the second part is a casted component forming an interface to the energy generating unit  33 . The casted component is stronger than the hollow tubular element and therefore suitable for carrying the load of the energy generating unit and the crane. 
     The energy generating unit  33  comprises an internal crane  34  handling a lifting rope  35 . The lifting rope is thereby attached to the load carrying structure via the interface between the energy generating unit  33  and the load carrying structure  31 ,  32 . 
     In  FIG. 4 , the lifting rope is attached to the crane and used for hoisting the crane from ground to the attachment point.  FIG. 4  illustrates an embodiment where the fixation structure is configured to interface the load carrying structure in a predetermined orientation, and where the crane is provided such that it can be lifted with the lifting rope attached to the fixation structure and such that it is in balance in a balance orientation matching the predetermined orientation. 
     The attachment point is, in this embodiment, a lower section of the second part  32  of the load carrying structure. 
     The crane illustrated in  FIG. 4  comprises a saddle shaped fixation structure  41  which matches the shape of the second part  32  of the load carrying structure, and due to the matching shapes, and the location of the lifting rope in the middle of the saddle, the saddle shape will guide the crane into the correct position on the load carrying structure. 
       FIG. 4  illustrates an embodiment wherein the fixation structure of the crane is configured for contact with the load carrying structure below a geometric centre of a cross section of the load carrying structure transverse to the outwards direction. Due to the saddle shape, the crane extends in contact with the load carrying structure from the point below the geometric centre to a point above the geometric centre where it is fixed by bolts via the bolt holes  42 . 
       FIG. 5  illustrates the crane when it is attached and  FIG. 6  illustrates when the crane is unfolded and ready to be used for handling large and heavy wind turbine components such as the entire energy generating unit or parts thereof. 
       FIG. 7  illustrates a crane where the internal power driven means  71  for driving the crane rope  72  is used also for hoisting the crane in the process of attaching the crane to the load carrying structure. In this embodiment, the crane rope  72  may constitute the lifting rope. The crane rope may be lifted to the load carrying structure e.g. by use of a small internal crane in the energy generating unit. 
     The crane illustrated in  FIG. 7  has a fixation structure configured for attaching a load carrying structure of an upside-down type wind turbine where the energy generating unit  81  is attached below the load carrying structure.  FIG. 8  illustrates the crane when attached to the load carrying structure  82 , and  FIG. 9  illustrates the crane when unfolded to an operational configuration. 
       FIG. 10  illustrates the load carrying structure  103 , including a first part  103 ′ and a second part  103 ″, the second part forming an axial termination of the first part and terminates the load carrying structure furthest away from the tower  102 . The first part is a hollow tube, and the second part is a casted component made of steel. The second part is therefore capable of withstanding larger impact and it can carry heavy components. The load carrying structure  103  acts as compression elements and it is supported by a tension element in the form of two guy wires  114  extending from a swivel arrangement  115  on the tower  102  to the second part  103 ″. The second part  103 ″ carries the energy generating unit  105  and is configured for carrying also the crane. 
     Example 1 
     In the following, use of the crane will be described with reference to a specific example and with reference to the  FIGS. 11-31 . In this example, the wind turbine has only a very limited lifting capacity. The illustrated procedure therefore includes two steps, firstly lifting and attaching a small crane, and secondly, using the small crane to attach a larger crane. 
     When doing a replacement of main components, a small jack-up barge will carry both an interim crane and a larger crane which is to be used for handling the components to the turbine.  FIGS. 11-14  illustrate a barge arriving at the wind turbine. The barge has no crane facility but carries the cranes which are to be fitted and used on the wind turbine. While the barge is being jacked-up, the technicians are loaded to the wind turbine. 
       FIG. 11  illustrates a jack up barge  110  being transported to the site of the wind turbine in question. The barge contains a small crane to be attached for interim work on the wind turbine.  FIG. 12  illustrates the barge being jacked up at the wind turbine site. 
       FIG. 13  illustrates the personnel enters the wind turbine, and  FIG. 14  illustrates that the personnel enters the load carrying structure and the site where the crane is to be attached. 
     When the barge has been jacked up, a small interim crane, e.g. of the brand ‘Tirak’, will be lifted to the load carrying structure. This procedure is illustrated in  FIGS. 15-18 . In the specific example, the interim crane is attached to a part of the load carrying structure referred to as “the bell”. The bell is a solid, moulded component arranged in coextension to a hollow shaft and it forms an interface to energy generating unit. The fixed installation tool is unfolded, and the small crane is lead through the tool, where it will fetch the hook of the mobile crane. 
       FIG. 15  specifically illustrates lifting of the winch part of a small interim crane.  FIGS. 16 and 17  illustrate that the small crane is prepared on the load carrying structure. In the enlarged view of  FIG. 16 a   , the components of the interim crane are shown. These are a power winch  161 , a crane arm  162  and a lifting lug  163 .  FIG. 17  specifically illustrates that the power winch  161  is arranged in the bell and that the arm  162  is arranged outside the bell. 
       FIG. 18  illustrates that the wire  180  of the interim crane is lowered to the deck of the barge. At this moment, the small crane constitutes an internal crane with an internal lifting rope and will be referred to as an internal crane in the following.  FIGS. 19-20  illustrate that the internal lifting rope  180  of the interim or internal crane is attached to the lifting lug  190  of the crane rope  191  of a crane  192  on the deck of the barge. The crane  192  on the deck of the barge is large relative to the internal or interim crane. The crane on the deck has a crane rope powered by a lifting power structure in the form of a powered winch. The crane rope is slackened, and the free end of the crane rope is connected to the internal lifting rope. The internal crane is subsequently applied for lifting the free end of the crane rope to the load carrying structure. This is illustrated in  FIG. 19  so that only the crane hook and cable are lifted by the internal or interim crane. 
       FIGS. 21-26  illustrate that the lifting lug  190  of the crane  192  is fixed to the load carrying structure.  FIG. 22  specifically illustrates the lifting lug being fixed to the arm  162  of the interim crane.  FIGS. 23 and 24  illustrate the crane  192  being lifted from the deck. In  FIG. 23 , it is illustrated that the crane rope  191  is winded up on the powered winch  230 , and the crane  192  starts lifting itself, with the build in crane winch. The operation can be radio controlled by the personnel being at the load carrying structure.  FIG. 26  illustrates that the crane  192  arrives at the load carrying structure. The Load carrying structure is constituted by the light weight arm  262 , the relatively strong bell,  260 , and the tension wires  261 .  FIG. 26  also clearly illustrates that the crane is thereby attached near the point where the tension wires  261  supports the load carrying structure. 
     When the crane has reached the top, the crane is bolted to the load carrying structure from the inside, i.e. from inside the hollow part of this structure. This is illustrated in  FIG. 27 . 
     Following this procedure, the lifting lug  190  is released from the arm  162 , c.f.  FIG. 28 . When the lifting lug  190  has been released, it can be used for lifting components which are to be handled. 
       FIGS. 29-31  illustrate that the crane is fixed to the turbine and can operate therefrom. In the illustration, it is shown that the crane can rotate from a downwards position to an operational, upwards, position, by using a build-in yaw system. 
     When the crane has reached an upwards position, the crane will unfold, and is now ready to start lifting and handling components for the wind turbine.