Patent Description:
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly or through a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.

A known way of mounting a wind turbine includes the steps of transporting the different elements to the site of the wind turbine. A wind turbine tower may typically comprise a plurality of tower sections which are mounted or stacked on top of each other. The tower sections may be joined to each other at tower flanges.

A large crane may be used to hoist subsequent tower sections and stack them on top of each other. After assembling the tower sections, the wind turbine nacelle may be lifted with the same large crane and can be mounted on top of the tower. Then the wind turbine rotor hub can be lifted with the crane and mounted to a rotor shaft and/or the nacelle.

Additionally, one or more blades are mounted to the wind turbine rotor hub. The rotor hub generally comprises a plurality of annular mounting flanges with openings. The blade can comprise a plurality of fasteners, such as bolts, or pins or studs at its blade root. During installation, these fasteners are to be fitted into the openings in the mounting flanges.

It is also known to hoist a complete rotor assembly, i.e. the hub with the plurality of blades, and mount it to e.g. the nacelle. But in order to mount a complete rotor assembly, a large surface area is required, which is typically not available e.g. in the case of offshore wind turbines.

It is further known to mount an incomplete rotor assembly on the nacelle, e.g. the hub with two blades and subsequently, mount the remaining blade. In these cases, the rotor with the two blades is normally mounted with the two blades pointing upwards, i.e. "bunny ears" configuration. There is thus no need for rotating the wind turbine rotor as the third blade could be vertically mounted from below. However, in order to be able to perform these operations, the prevailing wind speed has to be below a predetermined value for a prolonged period of time. The period of time depends on the expected length of the installation step and a safety factor to be taken into account.

It is also known to mount each of the plurality of blades in a substantially horizontal orientation or in a substantially vertical orientation. This means that individual installation steps may require less time and may be performed at higher winds, thus increasing the time windows available for installation.

Typically, to install a blade onto the wind turbine hub, the large crane previously used to install e.g. the tower, the nacelle and the rotor hub can be operated in order to raise the blade relative to the rotor hub. Unfortunately, it is expensive to operate such large cranes. In fact, the costs of employing such large cranes currently accounts for a significant portion of the overall costs associated with wind turbine installations. For offshore applications, special vessels carrying large cranes are required.

There is a clear tendency in the field to increase the size of the wind turbines. The wind turbine towers are built increasingly higher and the blades become increasingly longer. current tower designs are over <NUM>, <NUM> or even over <NUM> meters high. The weight of wind turbine components such as blades, nacelle, and rotor hub increases as well with an increase in size.

In order to mount tower sections on top of each other, and subsequently hoist a nacelle etc. ever larger cranes are required. Moreover, increasing counterweights are required for these large cranes.

There is a plurality of disadvantages related to the use of large cranes. Platform or pads for the cranes increase with an increase in size of the cranes. Transportation of crane components becomes increasingly complex and expensive. And large cranes are more sensitive to wind loads as well.

In view of these disadvantages, self-hoisting or climbing cranes have been proposed. Such climbing cranes offer several potential advantages including e.g. easier transportation of the crane, and regardless of the height of the tower the length of the crane does not need to be increased. The hoisting structure attached to a tower will also be less sensitive to wind loads. Also, using such self-hoisting or climbing cranes, the surface area required for installation stays substantially the same regardless of the height of the tower.

<CIT> discloses a crane assembly for erecting a tower including a plurality of tower sections, the crane assembly comprising a telescopic mast, a crane mounted on top of the telescopic mast and comprising lifting equipment, wherein the telescopic mast is configured to increase its length from a retracted state in an upwards direction, and comprises a clamp assembly for selectively gripping portions of the tower, and wherein the upper telescopic mast comprises a first base.

<CIT> discloses a method for onshore or offshore erecting an upstanding construction comprising longitudinal construction parts, in particular parts of a windmill. In this prior art document, each of the tower sections carries a guide facility which is depicted as rails. A crane can be guided along the rails.

<CIT> discloses a hoisting system for the installation of a wind turbine wherein said hoisting system comprises measures to achieve a load bearing connection to the tower of the wind turbine and comprises measures to move the hoisting system up and down along the tower wherein the hoisting system, when it is fixed to an already installed part of the wind turbine tower with said load bearing connection, is arranged to install or remove any of a tower section, a nacelle, a generator, a hub, and a blade in one or more combined hoists or in a single hoist.

Examples of the present disclosure provide methods and systems for erecting a tower, and particularly high wind turbine towers with long and heavy tower sections. Examples of the present disclosure provide methods and systems for erecting wind turbines which reduce bending loads in the crane assemblies.

In an aspect of the present disclosure, a crane assembly for erecting a tower including a plurality of tower sections is provided. The crane assembly comprises an upper telescopic mast and a lower telescopic mast connected to the upper telescopic mast and crane mounted on top of the upper telescopic mast and comprising lifting equipment. The upper telescopic mast is configured to change a length of the first telescopic mast, and comprises a first clamp assembly for selectively gripping portions of the tower. The lower telescopic mast is configured to change a length of the lower telescopic mast and comprising a second clamp assembly for selectively gripping portions of the tower. The upper telescopic mast is configured to increase its length from a retracted state in an upwards direction, and the second telescopic mast is configured to increase its length from a retracted state in a downwards direction.

In accordance with this aspect, a crane assembly is provided which is suitable for lifting relatively heavy and large components such as tower sections. The crane assembly according to this aspect comprises two telescopic masts which can extend in opposite directions. By selectively releasing the clamp assemblies of these telescopic masts and changing the lengths of the telescopic masts, the crane assembly can climb the tower. Moreover, the clamp assemblies may be suitably positioned at the moment of lifting tower sections to reduce loads in the crane assembly.

In a further aspect, a method for climbing a tower with a crane assembly is provided. The method comprises positioning a first tower section and attaching a crane assembly to the first tower section, the crane assembly comprising a telescopic mast and a crane mounted on top of the telescopic mast. The method further comprises stacking one or more further tower sections on top of the first tower section using the crane assembly and the crane assembly climbing the further tower sections by releasing a top clamp assembly of an upper telescopic mast and extending the upper telescopic mast and releasing a bottom clamp assembly of a lower telescopic mast and retracting the lower telescopic mast.

In yet a further aspect, a climbing crane assembly for use with a wind turbine tower is provided, which comprises a lower telescopic mast comprising a lower clamp assembly, an upper telescopic mast comprising an upper clamp assembly and mounted on top of the lower telescopic mast and a crane mounted on top of the upper telescopic mast and comprising lifting equipment. The lower telescopic mast is configured to increase its length by telescopically extending in a downwards direction, and the upper telescopic mast is configured to increase is length by telescopically extending in an upwards direction.

Each example is provided by way of explanation of the invention, not as a limitation of the invention.

Loads induced on the rotor blades <NUM> are transferred to the hub <NUM> via the load transfer regions <NUM>.

In examples, the rotor blades <NUM> may have a length ranging from about <NUM> meters (m) to about <NUM> or more. Rotor blades <NUM> may have any suitable length that enables the wind turbine <NUM> to function as described herein. For example, non-limiting examples of blade lengths include <NUM> or less, <NUM>, <NUM>, <NUM>, <NUM> or a length that is greater than <NUM>. As wind strikes the rotor blades <NUM> from a wind direction <NUM>, the rotor <NUM> is rotated about a rotor axis <NUM>. As the rotor blades <NUM> are rotated and subjected to centrifugal forces, the rotor blades <NUM> are also subjected to various forces and moments. As such, the rotor blades <NUM> may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position.

In the example, the wind turbine controller <NUM> is shown as being centralized within the nacelle <NUM>, however, the wind turbine controller <NUM> may be a distributed system throughout the wind turbine <NUM>, on the support system <NUM>, within a wind farm, and/or at a remote control center. The wind turbine controller <NUM> includes a processor <NUM> configured to perform the methods and/or steps described herein. Further, many of the other components described herein include a processor.

As used herein, the term "processor" is not limited to integrated circuits referred to in the art as a computer, but broadly refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific, integrated circuit, and other programmable circuits, and these terms are used interchangeably herein. It should be understood that a processor and/or a control system can also include memory, input channels, and/or output channels.

<FIG> is an enlarged sectional view of a portion of the wind turbine <NUM>. In the example, the wind turbine <NUM> includes the nacelle <NUM> and the rotor <NUM> that is rotatably coupled to the nacelle <NUM>. More specifically, the hub <NUM> of the rotor <NUM> is rotatably coupled to an electric generator <NUM> positioned within the nacelle <NUM> by the main shaft <NUM>, a gearbox <NUM>, a high-speed shaft <NUM>, and a coupling <NUM>. In the example, the main shaft <NUM> is disposed at least partially coaxial to a longitudinal axis (not shown) of the nacelle <NUM>. A rotation of the main shaft <NUM> drives the gearbox <NUM> that subsequently drives the high-speed shaft <NUM> by translating the relatively slow rotational movement of the rotor <NUM> and of the main shaft <NUM> into a relatively fast rotational movement of the high-speed shaft <NUM>. The latter is connected to the generator <NUM> for generating electrical energy with the help of a coupling <NUM>. Furthermore, a transformer <NUM> and/or suitable electronics, switches, and/or inverters may be arranged in the nacelle <NUM> in order to transform electrical energy generated by the generator <NUM> having a voltage between 400V to <NUM> V into electrical energy having medium voltage (<NUM> - <NUM> KV). Said electrical energy is conducted via power cables <NUM> from the nacelle <NUM> into the tower <NUM>.

The gearbox <NUM>, generator <NUM> in transformer <NUM> may be supported by a main support structure frame of the nacelle <NUM>, optionally embodied as a main frame <NUM>. The gearbox <NUM> may include a gearbox housing that is connected to the main frame <NUM> by one or more torque arms <NUM>. In the example, the nacelle <NUM> also includes a main forward support bearing <NUM> and a main aft support bearing <NUM>. Furthermore, the generator <NUM> can be mounted to the main frame <NUM> by decoupling support means <NUM>, in particular in order to prevent vibrations of the generator <NUM> to be introduced into the main frame <NUM> and thereby causing a noise emission source.

For positioning the nacelle <NUM> appropriately with respect to the wind direction <NUM>, the nacelle <NUM> may also include at least one meteorological measurement system which may include a wind vane and anemometer. The meteorological measurement system <NUM> can provide information to the wind turbine controller <NUM> that may include wind direction <NUM> and/or wind speed. In the example, the pitch system <NUM> is at least partially arranged as a pitch assembly <NUM> in the hub <NUM>. The pitch assembly <NUM> includes one or more pitch drive systems <NUM> and at least one sensor <NUM>. Each pitch drive system <NUM> is coupled to a respective rotor blade <NUM> (shown in <FIG>) for modulating the pitch angle of a rotor blade <NUM> along the pitch axis <NUM>. Only one of three pitch drive systems <NUM> is shown in <FIG>.

In the example, the pitch assembly <NUM> includes at least one pitch bearing <NUM> coupled to hub <NUM> and to a respective rotor blade <NUM> (shown in <FIG>) for rotating the respective rotor blade <NUM> about the pitch axis <NUM>. The pitch drive system <NUM> includes a pitch drive motor <NUM>, a pitch drive gearbox <NUM>, and a pitch drive pinion <NUM>. The pitch drive motor <NUM> is coupled to the pitch drive gearbox <NUM> such that the pitch drive motor <NUM> imparts mechanical force to the pitch drive gearbox <NUM>. The pitch drive gearbox <NUM> is coupled to the pitch drive pinion <NUM> such that the pitch drive pinion <NUM> is rotated by the pitch drive gearbox <NUM>. The pitch bearing <NUM> is coupled to pitch drive pinion <NUM> such that the rotation of the pitch drive pinion <NUM> causes a rotation of the pitch bearing <NUM>.

Pitch drive system <NUM> is coupled to the wind turbine controller <NUM> for adjusting the pitch angle of a rotor blade <NUM> upon receipt of one or more signals from the wind turbine controller <NUM>. In the example, the pitch drive motor <NUM> is any suitable motor driven by electrical power and/or a hydraulic system that enables pitch assembly <NUM> to function as described herein. Alternatively, the pitch assembly <NUM> may include any suitable structure, configuration, arrangement, and/or components such as, but not limited to, hydraulic cylinders, springs, and/or servomechanisms. In certain embodiments, the pitch drive motor <NUM> is driven by energy extracted from a rotational inertia of hub <NUM> and/or a stored energy source (not shown) that supplies energy to components of the wind turbine <NUM>.

The pitch assembly <NUM> may also include one or more pitch control systems <NUM> for controlling the pitch drive system <NUM> according to control signals from the wind turbine controller <NUM>, in case of specific prioritized situations and/or during rotor <NUM> overspeed. In the example, the pitch assembly <NUM> includes at least one pitch control system <NUM> communicatively coupled to a respective pitch drive system <NUM> for controlling pitch drive system <NUM> independently from the wind turbine controller <NUM>. In the example, the pitch control system <NUM> is coupled to the pitch drive system <NUM> and to a sensor <NUM>. During normal operation of the wind turbine <NUM>, the wind turbine controller <NUM> may control the pitch drive system <NUM> to adjust a pitch angle of rotor blades <NUM>.

According to an embodiment, a power generator <NUM>, for example comprising a battery, electric capacitors hence letter or an electrical generator driven by the rotation of the hub <NUM>, is arranged at or within the hub <NUM> and is coupled to the sensor <NUM>, the pitch control system <NUM>, and to the pitch drive system <NUM> to provide a source of power to these components. In the example, the power generator <NUM> provides a continuing source of power to the pitch assembly <NUM> during operation of the wind turbine <NUM>. In an alternative embodiment, power generator <NUM> provides power to the pitch assembly <NUM> only during an electrical power loss event of the wind turbine <NUM>. The electrical power loss event may include power grid loss or dip, malfunctioning of an electrical system of the wind turbine <NUM>, and/or failure of the wind turbine controller <NUM>. During the electrical power loss event, the power generator <NUM> operates to provide electrical power to the pitch assembly <NUM> such that pitch assembly <NUM> can operate during the electrical power loss event.

In the example, the pitch drive system <NUM>, the sensor <NUM>, the pitch control system <NUM>, cables, and the power generator <NUM> are each positioned in a cavity <NUM> defined by an inner surface <NUM> of hub <NUM>. In an alternative embodiment, said components are positioned with respect to an outer surface of hub <NUM> and may be coupled, directly or indirectly, to outer surface.

<FIG> schematically illustrates an example of a crane assembly in accordance with the present disclosure. The crane assembly <NUM> for erecting a tower including a plurality of tower sections, comprises a first telescopic mast <NUM>, a second telescopic mast <NUM> and a crane <NUM> mounted on top of the first telescopic mast and comprising lifting equipment. The first telescopic mast <NUM> is configured to change a length of the first telescopic mast <NUM>, and comprises a first clamp assembly <NUM> for selectively gripping portions of the tower. The second telescopic mast <NUM> is configured to change a length of the second telescopic mast <NUM> and comprises a second clamp assembly <NUM> for selectively gripping portions of the tower. The first telescopic mast <NUM> is configured to increase its length from a retracted state in a first direction <NUM>, and the second telescopic mast <NUM> is configured to increase its length from a retracted state in a second direction <NUM>. The second direction <NUM> is opposite to the first direction <NUM>.

In examples, the crane assembly <NUM> is configured to climb the tower by selectively releasing the first or second clamp assembly <NUM>, <NUM> and changing the length of the first and/or second telescopic masts <NUM>, <NUM>.

In the example of <FIG>, the first telescopic mast <NUM> comprises a first base <NUM>, and the second telescopic mast <NUM> comprises a second base <NUM>, and wherein the first base <NUM> is mounted on top of the second base <NUM>. The first base <NUM> may be bolted or otherwise attached to the second base <NUM>.

The first base <NUM> and second base <NUM> together may form a central mast segment. The length of the telescopic mast can thus be extended in two opposite directions, i.e. the first direction <NUM> when the first telescopic mast <NUM> is changed from a retracted state to a more extended state and in the second direction <NUM> when the second telescopic mast <NUM> is changed from a retracted state to a more extended state. Similarly the length of the telescopic mast can thus be shorted by returning the first and/or second telescopic mast <NUM>, <NUM> to a more retracted state.

In the example of <FIG>, the first telescopic mast <NUM> is configured to increase its length in an upwards direction <NUM>, and the second telescopic mast <NUM> is configured to increase its length in a downwards direction <NUM>.

The crane assembly <NUM> may further comprise a central clamp assembly <NUM> arranged with the first or the second base <NUM>, <NUM>. The central clamp assembly <NUM> may be arranged centrally between the first and second telescopic masts. The telescopic masts can change their length and move the upper clamp assembly <NUM> and the lower clamp assembly <NUM> upwards and downwards. An aspect of this example is that the central clamp assembly <NUM> may be arranged centrally between the upper and lower clamp assemblies <NUM>, <NUM> at different stages of the tower construction. This can allow heavy and long parts (e.g. tower sections) to be handled while maintaining bending loads in the crane assembly in an acceptable range.

In examples, the central clamp assembly <NUM> may be arranged to be displaceable along the first base <NUM> and the second base <NUM>. This aspect makes the crane assembly <NUM> more versatile and flexible, and allows suitably positioning the central clamp assembly <NUM> in different steps of the erection of a tower and installation of a wind turbine tower.

The central clamp assembly may be slidably arranged with respect to the first <NUM> and/or the second base <NUM>. Any suitable mechanism involving e.g. guides, rails, a rack and pinion mechanism, may be used to move the central clamp assembly with respect to the first <NUM> and/or the second base <NUM>.

As shown in <FIG>, the first telescopic mast <NUM> may further comprise one or more additional mast segments <NUM>, <NUM>, <NUM>, which are slidable with respect to the first base <NUM>. Similarly, the second telescopic mast <NUM> may also comprise one or more additional mast segments, <NUM>, <NUM>, <NUM> which are slidable with respect to the second base <NUM>.

A mechanism of increasing the length (by changing from a retracted state to a more extended state) and shortening the length (by changing from an extended state to a more retracted state) of the first and/or second telescopic masts may be e.g. hydraulic, or pneumatic. In each of the first and second telescopic masts, one or more hydraulic pistons or pneumatic pistons may be arranged.

The additional mast segments <NUM>, <NUM>, <NUM> (and <NUM>, <NUM>, <NUM>) include one or more intermediate segments <NUM>, <NUM> (and <NUM>, <NUM>), and a most distal segment <NUM> (<NUM>) that is arranged further away from the base <NUM> (<NUM>) than the intermediate segments <NUM>, <NUM> (and <NUM>, <NUM>), and the most distal segment <NUM> (<NUM>) includes the first clamp assembly <NUM>. The upper mast segment <NUM> includes an upper most segment <NUM> comprising the upper clamp assembly <NUM>. The lower mast segment <NUM> includes a lower most segment <NUM> comprising the lower clamp assembly.

The first clamp assembly <NUM> may be arranged at or near a distal end of the most distal segment <NUM>. Similarly, the second clamp assembly <NUM> may be arranged at or neat a distal end of the most distal segment <NUM>.

The crane <NUM> may be arranged on top of the most distal (most upper) segment <NUM>. A transition piece <NUM> of the crane may be bolted or otherwise attached to the distal end of segment <NUM>. The transition piece <NUM> forms a connecting piece between the telescopic mast(s) and the crane. A base (illustrated further in <FIG>) may be rotatably mounted on transition piece <NUM>. The base may comprise a frame <NUM> carrying a pneumatic or hydraulic mechanism <NUM> to change an orientation of boom <NUM> of the crane <NUM>. The boom <NUM> may be formed as a truss structure. At a most distal end <NUM> of boom <NUM>, lifting equipment (not further illustrated) may be arranged. The lifting equipment may include cables, ropes, pulleys, hooks and/or other suitable equipment.

<FIG> schematically illustrate details of an example of a crane assembly <NUM> attached to a tower comprising multiple tower sections, and more particularly of a second clamp assembly <NUM>, that is, in the example of <FIG>, the lower clamp assembly <NUM> of the lower telescopic mast <NUM>. The lower clamp assembly <NUM> is arranged at or near a distal end (lower most end) of the distal most segment (lower most segment) <NUM>.

The tower may comprise a first tower section <NUM> and a second tower section <NUM> mounted on top of the first tower section <NUM>. The first tower section <NUM> and the second tower section <NUM> are attached at mounting flanges at a junction <NUM> between the tower sections.

In the situation of <FIG>, the lower clamp assembly <NUM> is attached to pads <NUM>. The pads <NUM> in this example are arranged near a top end of first tower section <NUM>. In further examples, pads <NUM> may be arranged at or near a bottom end of tower sections.

The pads may be attached to or integrally formed with an outer wall of the tower section. The pads may include stiffeners supporting a substantially flat flange. The flat flange may include one or more holes <NUM> which can receive parts <NUM> of the clamping assembly for attaching and clamping the pads.

In examples, the second clamp assembly <NUM> comprises a first arm <NUM> including a first clamp <NUM> arranged at a distal end of the first arm <NUM>, and a second arm <NUM> including a second clamp <NUM> arranged at a distal end of the second arm <NUM>. The first and the second arms <NUM>, <NUM> may be telescopic arms. The first clamp assembly <NUM> at a distal end of the first telescopic mast (upper telescopic mast) may have a similar structure.

The first and/or the second clamp assembly <NUM>, <NUM> may be configured to change a distance between the first arm <NUM> and the second arm <NUM> such that the clamp assembly can grab (and release) pads of different tower sections. The different tower sections may have varying dimensions and in particular tower sections may be conical. In the example of <FIG>, the arms <NUM>, <NUM> may have a hydraulic mechanism <NUM> to extend the arms and retract the arms.

The clamps <NUM> may be rotatably mounted with respect to the first and second arms <NUM>, <NUM>. The clamps may be rotated around axis <NUM>. Clamps <NUM> may be hingedly mounted to column <NUM>. Rotation around axis <NUM> is one way in which a distance between clamps <NUM> of first and second arms <NUM>, <NUM> may be adjusted to adapt to changing distances between pads <NUM> on different towers and/or different tower sections.

The clamps <NUM> may comprise an engagement feature <NUM> which engages with the pad <NUM>, and in this particular example may be received in hole <NUM> of pad <NUM>. The coupling of the clamps to the pads may be a male-female coupling. By receiving engagement feature <NUM> in holes <NUM> the clamp may be securely fixed to the tower section. When such feature <NUM> is extracted, the clamp is released, and the corresponding telescopic mast segment may be moved upwards or downwards. The clamps <NUM> may be selectively activated and released using hydraulic mechanism <NUM>.

As may be seen in <FIG>, the lower clamp assembly <NUM> may include a central base <NUM> fitted around telescopic mast segment <NUM>. The central base may be welded to the telescopic mast segment. Other attachments may also be used.

<FIG> schematically illustrate details of crane <NUM> mounted on the upper telescopic mast <NUM>, and of upper clamp assembly <NUM> which may be arranged at or near a distal end of upper most segment <NUM> of the upper telescopic mast <NUM>.

The transition piece <NUM> may be partially conical or frustoconical. A lower end of transition piece <NUM> may be attached to an upper most segment <NUM> of the upper telescopic mast. The upper end may have increased dimensions, or an increased diameter compared to the lower end of the transition piece <NUM>. At the upper end of transition piece <NUM>, base plate <NUM> of crane <NUM> may be mounted. The base plate <NUM> may be rotatably mounted on transition piece <NUM> with e.g. a roller element bearing.

Frame <NUM> is mounted on base plate <NUM>. Hydraulic pistons <NUM> may change the orientation of boom <NUM> of crane <NUM>. By extending the hydraulic pistons <NUM>, the boom <NUM> may be positioned more vertically. By retracting the hydraulic pistons <NUM>, the boom may be positioned more horizontally and less vertically.

Boom <NUM> may be formed as a truss structure. And boom <NUM> may be rotated about axis <NUM> to change to a more horizontal or a more vertical position. In order to hoist tower sections, or other wind turbine parts and components, the base plate <NUM> may be rotated such that the boom points away from the tower. The hydraulic pistons <NUM> may be adapted to rotate the boom <NUM> to a more horizontal position, such that distal end <NUM> of crane <NUM> is further away from the (partially constructed) tower. Lifting equipment arranged with the distal end <NUM> of the crane may be used for hoisting a wind turbine component. Once hoisted to the top of the tower, the boom may be rotated towards a more vertical position, and the base plate <NUM> may then be rotated such that the component (tower section or other) may be mounted.

The upper clamp assembly <NUM> is illustrated in <FIG>. The upper clamp assembly <NUM> may generally be similar in terms of functionality and structure to the lower clamp assembly <NUM> illustrated in <FIG>.

The upper clamp assembly <NUM> may have a first arm <NUM>, and a second arm <NUM>. The length of the arms may be adapted, e.g. the arms <NUM>, <NUM> may be telescopic. The length of the arms may be regulated using e.g. a hydraulic or pneumatic mechanism. At the distal ends of the arms <NUM>, <NUM>, clamps <NUM> are arranged. Similarly to what was shown in <FIG>, the clamps <NUM> may be hingedly mounted and may be rotatable about vertical axis <NUM>. A hydraulic mechanism <NUM> may be provided to control positions of the clamps. As illustrated with respect to the lower clamp assembly, a hydraulic (or pneumatic) mechanism may be used for activating and releasing clamps <NUM>.

<FIG> schematically illustrate a central clamp assembly <NUM> of the example of crane assembly <NUM>. The central clamp assembly <NUM> may include two sets of "central clamps", <NUM>, <NUM>. The two sets of central clamps include two upper (central) clamps <NUM> and two lower (central) clamps <NUM>. <FIG> illustrate a longitudinal cross-sectional view and therefore only show a single upper clamp <NUM> and a single lower clamp <NUM>.

Upper clamps <NUM> and lower clamps <NUM> may be used for selectively gripping portions of a tower, and more particularly to selectively clamp and release pads <NUM> arranged at different heights of the tower. The clamps <NUM>, <NUM> are generally similar to the clamps of the upper and lower clamp assemblies. The mechanism and coupling of the clamps may be similar since they are configured to grip the same pads <NUM> as the lower and upper clamp assemblies. The upper and lower clamps <NUM>, <NUM> of the central clamp assembly <NUM> may therefore comprise engagement features <NUM> and <NUM> respectively which are configured to engage with the same holes on pads along the tower. These engagement features <NUM>, <NUM> may therefore be similarly sized and shaped and work in the same manner as engagement features <NUM> described hereinbefore with reference to <FIG>.

The central clamp assembly <NUM> may comprise a central ring <NUM> which is configured to be fitted around a base <NUM> of the first (upper) telescopic mast segment and/or a base <NUM> of the second (lower) telescopic mast segment. The central clamp assembly <NUM> may further include a frame <NUM> attached to central ring <NUM> and extending radially away from the telescopic mast segments. Frame <NUM> may include a truss structure and a column <NUM>. The clamps <NUM>, <NUM> may be rotatably mounted around vertical axes in a similar manner as described before.

The central clamp assembly <NUM> may be configured to be displaced along a height of the second base <NUM>, and/or the first base <NUM>. The second base and first base <NUM> may have the same diameter, and the central clamp assembly <NUM> may be slidably arranged along an outside of the first and second base <NUM>, <NUM>.

A distance between upper clamps <NUM> and lower clamps <NUM> may be different from the distance between the clamps <NUM> of the upper clamp assembly <NUM> and of the clamps <NUM> of the lower clamp assembly <NUM>. In particular, the distance between clamps <NUM>, <NUM> may be smaller than the distance between the clamps <NUM> and <NUM>. In use, the clamps of the central clamp assembly may be arranged "within" the clamps <NUM>, or <NUM>. When clamps <NUM> grip pads <NUM> at a given height, the upper clamps <NUM> of central clamp assembly may be moved upwards and may then be clamped to the same pads e.g. using holes <NUM> which are arranged closer to each other than holes occupied by clamps <NUM>. Then, the upper clamps may be released, and the upper telescopic mast may be moved further upwards for a next step in the construction or erection of the tower or a wind turbine. Similarly, the central clamp assembly <NUM> in use may be lowered to clamp pads <NUM> which are gripped by lower clamps <NUM>. After securing the pads <NUM> with the central clamp assembly, the lower clamp assembly may be released, and the lower telescopic mast may be extended downwards, e.g. in a descending operation after completion of the tower.

As schematically illustrated, the telescopic mast segments <NUM>, <NUM> may include one or more hydraulic cylinders <NUM>, <NUM> and pistons <NUM>, <NUM> to change the length of the telescopic mast segments.

In an aspect of the present disclosure, a climbing crane assembly for use with a wind turbine tower is thus provided. The climbing (or "self-hoisting") crane assembly comprises a lower telescopic mast comprising a lower clamp assembly, an upper telescopic mast comprising an upper clamp assembly and mounted on top of the lower telescopic mast and a crane mounted on top of the upper telescopic mast and comprising lifting equipment. The lower telescopic mast is configured to increase its length by telescopically extending in a downwards direction, and the upper telescopic mast is configured to increase is length by telescopically extending in an upwards direction.

The climbing crane assembly may further comprise a central clamp assembly. And the central clamp assembly may be displaceable along the lower telescopic mast and the upper telescopic mast.

The climbing crane assembly may comprise a first set of central clamps, and a second set of central clamps, the first set of central clamps being arranged at a different vertical position than the second set of central clamps.

The crane may be rotatably mounted with respect to the upper telescopic mast.

With examples of the climbing crane assemblies as described herein, a method according to a further aspect of the present disclosure is enabled. In a further aspect, the present disclosure provides a method for climbing a tower <NUM> with a crane assembly <NUM>. The method comprises positioning a first tower section <NUM> and attaching a crane assembly <NUM> to the first tower section <NUM>. The crane assembly <NUM> comprises a telescopic mast and a crane <NUM> mounted on top of the telescopic mast. The method further comprises stacking one or more further tower sections <NUM> (and other). on top of the first tower section <NUM> using the crane assembly <NUM>. And the method further comprises the crane assembly <NUM> climbing the further tower sections <NUM> (and other) by releasing a top clamp assembly <NUM> of an upper telescopic mast <NUM> and extending the upper telescopic mast <NUM> and releasing a bottom clamp assembly <NUM> of a lower telescopic mast <NUM> and retracting the lower telescopic mast <NUM>.

The crane assembly <NUM> climbing the tower may further comprise releasing a central clamp assembly <NUM>, displacing the central clamps assembly <NUM> upwards relative to the upper telescopic mast <NUM> and/or the lower telescopic mast <NUM> and gripping a portion <NUM> of the tower <NUM> with the central clamp assembly <NUM>.

The methods may further comprise hoisting a tower section <NUM> (and other) while the central clamp assembly <NUM> grips a portion <NUM> of the tower <NUM> and is positioned substantially at a same distance from the lower clamp assembly <NUM> and the top clamp assembly <NUM>.

<FIG> schematically illustrate a method of erecting a wind turbine tower and a wind turbine. In <FIG>, a bottom tower section <NUM> is mounted on a foundation. The bottom tower section <NUM> may include pads <NUM> near an upper end <NUM> of bottom tower section <NUM> and pads <NUM> near a lower end <NUM> of tower section <NUM>. Pads <NUM> and <NUM> are configured for gripping by clamps of crane assembly <NUM>. As discussed previously, the crane assembly <NUM> includes a first (or upper) telescopic mast segment <NUM>, a second (or lower) telescopic mast segment <NUM>, and a central clamp assembly <NUM>. The first telescopic mast includes a first (or upper) clamp assembly <NUM>, and the second telescopic mast includes a second (or lower) clamp assembly <NUM>. The crane assembly <NUM> further includes a crane <NUM>.

In the situation illustrated in <FIG>, the bottom clamp assembly <NUM> may grip pads <NUM>, and the lower central clamps of the central clamp assembly <NUM> may grip pads <NUM>. Crane <NUM> may be used to hoist a further tower section <NUM>.

In the situation illustrated in <FIG>, both the upper telescopic mast <NUM>, and the lower telescopic mast <NUM> are both in their retracted position i.e. the crane assembly <NUM> has its most retracted (shortest) configuration.

In <FIG>, second tower section <NUM> is stacked on top of the bottom tower section <NUM>. Tower section <NUM> includes a bottom end <NUM> and an upper end <NUM>. Tower section <NUM> is attached at its bottom end <NUM> to tower section <NUM>. Near its upper end <NUM>, pads <NUM> for further gripping are arranged. After stacking the second tower section <NUM> on top of section <NUM>, the upper clamp assembly <NUM> may grip pads <NUM>.

In <FIG>, crane <NUM> may have been used to stack a further tower section <NUM> on top of tower section <NUM>. Bottom end <NUM> of tower section <NUM> may be attached to top end <NUM> of tower section <NUM>. Pads <NUM> may be provided near a top end of section <NUM>.

The upper clamp assembly <NUM> may be released from pads <NUM>. After this release, the upper telescopic mast <NUM> may be extended from is retracted state to a more extended state. In the extended state, several telescopic segments <NUM>, <NUM>, <NUM> of the upper telescopic mast are more visible. When the upper clamp assembly <NUM> reaches pads <NUM>, as may be seen in <FIG>, the clamps of the upper clamp assembly may grip pads <NUM>.

<FIG> illustrates that a further tower section <NUM> has been stacked on top of tower section <NUM>. Near a top end <NUM> of the tower section <NUM>, pads <NUM> for further gripping in different steps may be arranged.

In <FIG>, the central clamp assembly <NUM> has been released from pads <NUM> and has been moved upwards to approach pads <NUM>. The central clamp assembly in this respect may be moved upwards by displacing the central clamp assembly <NUM> along the telescopic mast segments <NUM>, <NUM>, and the lower telescopic masts <NUM> has been extended to a more extended state, showing base <NUM>, and segments <NUM>, <NUM> and <NUM>.

The central clamp assembly <NUM> may then grip the pads <NUM> which are gripped by the upper clamp assembly <NUM>. The clamps <NUM> may grip portions of the pads on an inside with respect to where the upper clamp assembly grips pads <NUM>.

Then, as shown in <FIG>, the upper telescopic masts <NUM> may be extended upwards. The upper clamp assembly may reach pads <NUM> near an upper end <NUM> of tower section <NUM> and grip these pads.

In <FIG>, the lower telescopic mast <NUM> may be retracted and thus moved upwards to reach pads <NUM> at an upper end of tower section <NUM>. One aspect of the telescopic mast with independent telescopic segments and which are extendable in opposite directions means that the central clamp assembly <NUM> may be positioned somewhat centrally between the upper clamp assembly <NUM> and the lower clamp assembly <NUM> such that bending loads in the crane assembly <NUM> are maintained under control.

In <FIG>, the next tower section <NUM> is then positioned and mounted on top of tower section <NUM>. The further steps in the erection of the tower <NUM> may continue in a similar manner.

In <FIG>, the central clamp assembly <NUM> has been moved upwards, the lower telescopic mast has been extended, and so has the upper telescopic mast such that pads <NUM> at the top of tower section <NUM> can be reached.

In <FIG>, a further tower section <NUM> may be positioned and mounted on tower section <NUM>. As for the other tower sections, tower section <NUM> may include pads <NUM> at an upper end of the tower section.

In <FIG>, the lower telescopic mast <NUM> has been retracted such that the lower clamp assembly <NUM> reached pads <NUM> of tower section <NUM>. In <FIG>, the central clamp assembly <NUM> has been moved upwards such that the central lower clamps, rather than the central upper clamps, grip pads <NUM>.

<FIG> illustrate further steps in the method of erecting tower <NUM> in which the crane assembly <NUM> climbs tower <NUM>.

Finally, <FIG> illustrate that the same crane assembly <NUM> may be used to hoist top tower section <NUM>, and nacelle <NUM>. In this example, hub <NUM> may be hoisted and attached at a front side of the nacelle <NUM> (<FIG>). Subsequently, individual blades may be hoisted and attached to the hub <NUM>. In this example, blades <NUM> are mounted to the hub in a substantially horizontal orientation (either at a <NUM> o'clock or a <NUM> o'clock position of the hub). In yet further examples, one or more blades may be attached to the hub and the assembly may be hoisted.

In <FIG>, the installation of the wind turbine has been completed. Then, the crane assembly <NUM> may descend the tower <NUM> by selectively gripping portions of the tower, releasing portions of the tower, and extending and retracting telescopic masts <NUM>, <NUM>.

Within the scope of the present disclosure, the dimensions of the several elements of the crane assembly <NUM> and of the tower <NUM> and of the tower sections, <NUM>, <NUM>, <NUM> etc. may be varied. In general, the dimensions of the crane assembly <NUM> may be adapted to a certain extend to the tower <NUM> to be erected. On the other hand, the upper and lower telescopic masts provide versatility and flexibility in this respect.

In examples, a diameter of the base <NUM>, <NUM> of the telescopic masts may be e.g. between <NUM> and <NUM> meters. The length of segments <NUM>, <NUM>, <NUM>, <NUM> and segments <NUM>, <NUM>, <NUM>, <NUM> in the most retracted state may be e.g. between <NUM> and <NUM> meters. In examples, the upper telescopic mast <NUM> may have the same or similar dimensions as the lower telescopic mast <NUM>. In other examples, the upper and lower telescopic masts may be different in size and may comprise different numbers of segments.

Claim 1:
A crane assembly (<NUM>) for erecting a tower including a plurality of tower sections, the crane assembly (<NUM>) comprises:
an upper telescopic mast (<NUM>);
a lower telescopic mast (<NUM>) connected to the upper telescopic mast (<NUM>); and
a crane (<NUM>) mounted on top of the upper telescopic mast (<NUM>) and comprising lifting equipment; wherein
the upper telescopic mast (<NUM>) is configured to increase its length from a retracted state in an upwards direction (<NUM>), and comprises a first clamp assembly (<NUM>) for selectively gripping portions of the tower, and
the lower telescopic mast (<NUM>) is configured to increase its length from a retracted state in a downwards direction (<NUM>) and comprises a second clamp assembly (<NUM>) for selectively gripping portions of the tower, and
wherein the upper telescopic mast (<NUM>) comprises a first base (<NUM>), and the lower telescopic mast (<NUM>) comprises a second base (<NUM>), and wherein the first base (<NUM>) is mounted on top of the second base (<NUM>).