A method for optimizing hoisting performance of a wind turbine hoisting system.

Abstract

The present invention presents a method for optimizing hoisting performance of components in situ using an up- tower crane (1) mounted in or on a wind turbine (11) nacelle (8). The method reduces the operation complexity, time consumption and costs of hoisting before, during and after the hoisting procedure and at the same time narrow down the working location to a minimum. A wind turbine (11) comprises a tower (12) and a nacelle (8) having a hub (9) end and a hoisting system comprises an up- tower crane (1) arranged in or on the nacelle (8), wherein the up- tower crane (1) is configured to hoist a component (13) according to a load rating chart. The lifting capacity of the up- tower crane (1), in cooperation with the wind turbine (11), is defined by the load rating chart. The load rating chart defines a plurality of hoisting zones (5,10,30,31,50,51) having different lifting capacity. The up- tower crane (1) comprises a crane boom (3) and a main wire having a hook arrangement (4, 14). The up- tower crane (1) is configured to yaw into at least one crane (1) yaw position. The method comprises the following acts of: - selecting at least one of said plurality of hoisting zones (5,10,30,31,50,51), - determining a first nacelle (8) yaw position of said nacelle (8), - determining a first load position of said component (13), - yawing said up- tower crane (1) to a first crane (1) yaw position, such that said crane boom (3) extends in a boom direction of the nacelle (8)'s hub (9) end within a predetermined hoisting zone (5), wherein the crane boom (3) is arranged in a first booming position, - yawing said nacelle (8) into a second nacelle (8) yaw position different than said first nacelle (8) yaw position, while keeping the up- tower crane (1) in said first crane (1) yaw position relative to the hub (9) end, - hoisting said component (13) from said first load position to a second load position.

Description

[0001] A method for optimizing hoisting performance of a wind turbine hoisting system.

[0002] Field of invention

[0003] The present invention relates to a method for optimizing hoisting performance of components in situ using an up-tower crane mounted in or on a wind turbine nacelle.

[0004] Background of the invention

[0005] As wind turbines become larger and heavier, the requirement for hoisting components is also increasing. For example, a hoisting operation for hoisting larger components or other equipment demands cranes, having larger lifting capacity. The increased size and / or weight of said components or other equipment also demands a safe and stable control to avoid hazardous situations. The wind is an important factor when hosting said components or other equipment, especially when hoisting rotor blades, which is very sensitive to wind condition. Handling a heavy component is complicated and there is an increased risk of damage both said components being hoisted and the tower or nacelle, or in worst case scenario, the workers may be seriously injured.

[0006] Some of the components are very long, such as rotor blades. This may require a very large operation location, and very large crane equipment to handle rotor blades on site. Not every location has an optimal area, and over time the location may have change, such as being overgrown and impassable. This complicate maintenance tasks considerably, especially when using only an up-tower crane. A smaller up-tower crane may not provide the lifting capacity needed, when the crane boom must extend beyond the nacelle’s hub, when the wind turbine is in parked or locked mode. This requires larger up-tower cranes having a required lifting capacity far beyond the hub.

[0007] Alternatively, the onshore locations must have a large available area, where it is possible to e.g., sliding and lay down a rotor blade. Such area must often be two or more times the length of the rotor blade for sliding the rotor blade down using cables and taglines. If the wind turbine is located in an offshore environment, the tasks are much more complicated.

[0008] The hoisting procedure are often accompanied by using a plurality of winch systems, which are arranged on the ground at a distance from the wind turbine tower. Further available area is needed for hosting the winch systems, which is required for the operation, and which is arranged far away from the wind turbine tower. The winch cable is attached to the component or other equipment or if preferred attached to the yoke or similar, to provide an assisting control of the movement of the component or other equipment during hoisting. Often the winch systems are arranged in a substantially far distance to the tower and to each other to provide a common assisting control of the movement. If the wind turbine tower is placed in a location having a hilly terrain with trees or rocks, the accessibility will be complicated. It will also be complicated, and in some situations even impossible to provide a common assisting control using two or more winch systems. The entire task of hoisting components or equipment in a secure manner, using a crane and winches, is complicated, time consuming and expensive.

[0009] During maintenance of a wind turbine, the wind turbine is set in a parked mode, such that the wind turbine does not move unintentionally. During maintenance tasks, it’s essential to prevent any unintended wind turbine movement for safety reason. For example, the rotor system and the yaw system of a wind turbine are typically locked down to keep the rotor blades and nacelle in a fixed position. A yaw brake or other brakes if provided are engaged, when the wind turbine is shut down for maintenance, to ensure that the nacelle remains stationary during work. In some cases, physical locks or pins are inserted into the rotor or yaw drive mechanism to prevent movement of the rotor or nacelle. These locks ensure that the nacelle remains fixed during maintenance tasks only activated, when testing a specific functional feature. The workers follow strict safety procedures during maintenance. The workers verify that the yaw system is secured before entering the nacelle. Additionally, they may visually inspect the yaw brake and confirm its engagement. Up-towers cranes are often accessed from the nacelle, and the up-tower cranes may be operated by workers in the nacelle. The yaw system, as well as the rotor system, is secured before operating the up-tower crane or cranes. The up-tower cranes which are arranged in or on wind turbines must meet the increasing requirements of lifting and lowering larger components in a safe and secured manner to avoid any hazardous situation. The up-tower cranes must be larger and have a larger lifting capacity, because said components are getting larger, heavier and more susceptible to wind impact. Since the wind turbine is getting larger, the crane boom must reach further away to extend beyond the wind turbine to avoid damaging the nacelle or tower during operation. The up-tower crane must provide a lifting capacity, according to the load rating chart for hoisting heavy components in a safe and secure manner. The lifting capacity must be increased as the wind turbine’s components and equipment are getting larger as well. This increases the costs for larger up-tower cranes.

[0010] The document WO2022 / 217362 Al, discloses a method for dismounting or mounting a rotor blade of a wind turbine. The method supports a rotor blade of a wind turbine with a ground-based lift system and a nacelle-mounted lift system, arranged at a tip-side position on the rotor blade in relation to a center of gravity of the rotor blade in a distance from the wind turbine tower. The rotor blade is supported by the ground-based lift system at the tip end of the rotor blade. The nacelle-mounted lift system is in a substantially non-vertical orientation with respect to the ground, when separating the rotor blade from or connecting the rotor blade to a rotor hub of the wind turbine. The method described in the document needs two systems to hoist a rotor blade which makes the process of hoisting very costly. The ground-based lift system and a nacelle-mounted lift system are very sensitive to the ambient conditions when hosting a rotor blade.

[0011] Summary of the invention

[0012] It is an object of the present invention to overcome these problems by providing a method for optimizing hoisting performance of hoisting components related to a wind turbine using an up-tower crane, and at the same time narrow down the working location to a minimum.

[0013] It is a further object of the present invention to provide a method for reducing the operation complexity, time consumption and costs of hoisting before, during and after the hoisting procedure.

[0014] A hoisting system which uses an up-tower crane for hoisting components to and from a wind turbine often offers several benefits, especially during installation and maintenance. Up-tower cranes may be structurally bolted to the wind turbine, enhancing stability and safety during lifting operations. Up-tower cranes take up less space on the hardstand, where the crane is positioned, and still when assembling wind turbines, up-tower cranes provide precise coordination during lifting, which enables more efficient lifting operations. The use of up-tower cranes are a cost-effective solution for hoisting operations both on-shore as well as off-shore. It is important to keep the up- tower cranes cost-effective, and optimize the up-tower cranes’ efficiency, even though the wind turbines are getting larger and the hoisting operations more complex. Especially replacing rotor blades may require the need for optimized hoisting performance, such that the up-tower cranes provide the lifting capacity needed. The up-tower crane is often attached to the nacelle behind the hub. The up-tower crane’s load rating chart is defined by the placement of the up-tower crane relative to the wind turbine construction. The lifting capacity must be taken into consideration, when the up-tower crane hoists components.

[0015] The present invention addresses this by providing a method for optimizing hoisting performance of a wind turbine hoisting system, wherein said wind turbine comprises a tower and a nacelle having a hub end, wherein said hoisting system comprises an up-tower crane arranged in or on the nacelle, wherein the up-tower crane and the wind turbine in cooperation defines a load rating chart having a plurality of hoisting zones, wherein said up-tower crane comprises a crane boom and a main wire, wherein the up-tower crane is configured to yaw into at least one crane yaw position, wherein the main wire having a hook arrangement, wherein the up-tower crane is configured to hoist a component according to said load rating chart, wherein the component has a first axis, wherein the method comprises the following acts of: selecting at least one of said plurality of hoisting zones, determining a first nacelle yaw position of said nacelle, determining a first load position of said component,

[0016] - yawing said up-tower crane to a first crane yaw position, such that said crane boom extends in a boom direction of the nacelle’s hub end within a predetermined hoisting zone, wherein the crane boom is arranged in a first booming position,

[0017] - yawing said nacelle into a second nacelle yaw position different than said first nacelle yaw position, while keeping the up-tower crane in said first crane yaw position relative to the hub end, hoisting said component from said first load position to a second load position.

[0018] To avoid the need for larger up-tower cranes having longer crane booms, the up-tower crane may use the nacelle to provide a larger lifting capacity during hoisting operation. The up-tower crane has a large lifting capacity in front of the nacelle’s hub end. The up-tower crane is advantageously configured to hoist a component in cooperation with the wind turbine. When the up-tower crane is cooperating with the nacelle’s position during hoisting operation, wherein the lifting capacity of the hoisting system will be optimized, while working within a high lifting capacity hoisting zone determined from the load rating chart. The up-tower crane is advantageously configured to hoist a component in cooperation using the nacelle’s yaw system, to move the crane boom into a desired hoisting position, and still keeping the up-tower crane in the high lifting capacity hoisting zone according to the load rating chart. This way it will be possible for the hoisting system to hoist heavy wind turbine components or other equipment, when cooperating with the entire wind turbine construction.

[0019] The hoisting system comprises an up-tower crane, which is attached to the nacelle. The up-tower crane comprises a crane boom and main wire. The tip of crane boom may extend beyond the hub of the nacelle, such that the main wire can be arranged in front of the hub end or beside of the hub end of the nacelle. A hook arrangement may be attached to a hook end of the main wire. The hook arrangement is configured to be attached to a wind turbine components or other required equipment. In the following, the wind turbine components or other required equipment will be referred to as component or components. For example, the hook arrangement may be a rotor blade hook arrangement or a hub hook arrangement etc. The up-tower crane is configured to hoist at least one component within a hoisting zone. The hoisting zone may be a limited hoisting zone, which is chosen from the load rating chart, preferably within a hoisting zone having a high lifting capacity. In the load rating chart, the up-tower crane’s positions are divided into a plurality of hoisting zones, wherein each hoisting zone may refer to different load capacities. The hoisting zone with the largest lifting capacity is extending in front to the nacelle’s hub end.

[0020] The method comprises acts, wherein the order of the acts or some of the acts may be arbitrary. The order of acts may depend on the hoisting operation. It is important to select a hoisting zone according to the load rating chart, based on the component’s weight and if preferred the component’s dimension, and if preferred the ambient conditions. The nacelle’s yaw system is activated for hoisting use, such that the nacelle is capable of being yawed into a plurality of nacelle yaw positions before, during and after hoisting a component. The first nacelle yaw position of the nacelle may be determined or selected, such that up-tower crane is capable of being yawed to a predetermined first crane yaw position relative to the nacelles first nacelle yaw position. The crane boom is yawed into the first crane yaw position using the up-tower cranes yaw system, such that the crane boom is capable of extending in a boom direction relative to the nacelle’s hub end. The crane boom is arranged within the predetermined hoisting zone having a predetermined booming position. The crane boom’s booming position may be altered during hoisting operation. The up-tower crane may mostly operate within the hosting zones having the highest lifting capacity. The up-tower crane may have a minor variable working space, which deviates from the optimal position, if needed.

[0021] The first load position of the component may also be determined, such that when yawing the nacelle into a second nacelle yaw position different than the first nacelle yaw position, the second nacelle yaw position may be relative to the first load position of the component. When the nacelle is yawed into the second nacelle position the crane boom in the first crane yaw position relative to the hub end. A rotor hub, also described as a hub, may be attached to the hub end. The crane boom is moved into position relative to the first load position of the component using the nacelle’s yaw system. The up-tower crane in cooperation with the wind turbine is then capable of hoisting the component from a first load position to a second load position, in a safe and secure manner.

[0022] The up-tower crane may be a crane system. The up-tower crane may be a crane system comprising more than one up-tower crane. The up-tower crane system may comprise one crane base having more than one crane booms. The up-tower crane system may comprise more than one crane base. Each crane base may comprise one or more crane booms. At least one of the crane booms may hoist a component in a predetermined hoisting zone with a high lifting capacity. In an advantageous method of the invention, the method comprises one or both of further acts:

[0023] - yawing the nacelle to a third nacelle yaw position different from the second nacelle yaw position,

[0024] - moving the crane boom to a second booming position different from the first booming position, while keeping said up-tower crane in the first crane yaw position, such that crane boom is arranged within in the predetermined hoisting zone.

[0025] The base of the up-tower crane may be attached in or on the nacelle. The crane boom is extending from the up-tower crane’s tower or base passing the nacelle’s hub end, such that the hook end of the main wire may be arranged on the opposite side of the nacelle’s hub end or if present the hub. The nacelle may be parked in a predetermined or arbitrary parked position, e.g., to be ready for maintenance or inspection. When starting the hoisting operation, the nacelle is the yawed into a first nacelle yaw position. Alternative the first nacelle yaw position may be the parked position. The crane boom is arranged in a first boom yaw position, wherein the crane boom is arranged in a first booming position. The main wire’s hook end is in front or on one or both of the opposite sides of the nacelle hub end, holding the hook arrangement. The crane boom may be arranged in a predetermined boom yaw position before first boom yaw position. Alternatively, the first boom yaw position is the predetermined boom yaw position. During operation, the nacelle may be moved from a second nacelle yaw position to a third nacelle yaw position. The third nacelle yaw position is different that the second nacelle yaw position. The third nacelle yaw position may be similar to the first nacelle yaw position. Further nacelle yaw position may be optional during the hoisting operation. The crane boom may be moved from a first booming position to a second booming position different from the first booming position. Further booming positional may be optional during hoisting operation. While booming the crane boom into different booming positions, the crane boom may be in the first crane yaw position relative to the hub end of the nacelle in the predetermined hoisting zone.

[0026] The hook arrangement may comprise a yoke device. The yoke device, which may hang from the main wire’s hook end, is capable of being attached to the component, e.g. a rotor blade, rotor or other parts of the wind turbine. When the yoke device may for example be attached to the rotor blade, wherein the yoke device and the rotor blade forms a combined load, which has a combined center of gravity when being hoisted. The yoke device and the rotor blade may be adjusted relative to each other, and thereby changing the position of the combined center of gravity. Taglines may be attached to the rotor blade or to the hook arrangement. The position of the combined center of gravity may also be displaced if taglines are adjusted relative to each other, or if preferred to the main wire. The taglines may pull the rotor blade or keep the rotor blade in a preferred hoisting position. The hoisting position may change during the hoisting procedure.

[0027] The hook arrangement may furthermore comprise a carry arrangement, which may be placed between the main wire’s hook end and the yoke device, to avoid interferences or collision between the main wire and the hub, during operation. The position of the combined center of gravity may also be displaced if the taglines are adjusted relative to carry arrangement, and if present the yoke device.

[0028] In a further method of the invention, the method comprises further act of determining the crane boom’s booming position relative to the length of the main wire, when hoisting said component from said first load position to said second load position.

[0029] The crane boom’s booming position may be determined based on the length of the main wire. The crane boom’s booming position may also be determined based on the length of the main wire relative to the tagline force acting on the component, when the tagline may pull the component during hoisting. When the tagline force acting on the component an indirect weight may be added to the component. The length of the wire is an additional weight of the wire the up-tower crane has to carry from the tip end of the crane boom beside the weight of the component to hoist, when hoisting the component from the first load position to the second load position. If the length of the main wire is short the additional main wire weight is reduced, an increased tagline force, if present, may act on the component adding an increased tagline weight to a total load weight of the component, the main wire and the tagline during hoisting. If the length of the main wire is long, a reduced tagline force, if present, may act on the component adding a reduced tagline weight to a total load weight of the component, the main wire and the tagline during hoisting. The tip of the crane boom may be in one hoisting zone have a first length of main wire, and if the tip of the crane boom moves to an adjacent hoisting zone or changing the angle of the booming position, the main wire may be altered to a second length. This way the weight of the main wire and if present taglines may be taken into consideration when determining the total load weight to be hoisted according to the load rating chart.

[0030] In a further method of the invention, the method comprises one or more of further acts of: determining one or more nacelle yaw positions from at least one ambient condition acting on the component, determining the crane boom’s booming position from at least one ambient condition acting on the component.

[0031] Ambient condition information may be retrieved. The ambient condition may be wind condition. The forces of the wind may act more or less on the component during hoisting. The wind may drag the component, such that the weight of the component appears increased. In such situation, the lifting capacity may be taken into consideration while hoisting the component. The wind condition may be predicted, such that the effect on the component can be estimated in advance.

[0032] The nacelle yaw position may be altered relative to the one ambient condition, such that the impact of the ambient condition may be reduced to a minimum. Depending on the shape of the component, and how sensitive the component is to the ambient condition, the nacelle yaw position may be determined from the ambient condition’s impact on the component based on the component’s dimension and weight.

[0033] The crane boom’s booming position may be altered relative to the one ambient condition, such that the impact of the ambient condition may be reduced to a minimum. Depending on the shape of the component, and how sensitive the component may be to the ambient condition, the crane boom’s booming position may be determined from the ambient condition’s impact on the component based on the component’s dimension and weight. In a still further method of the invention, wherein arranging the rotor blade in a rotated angled position between + / - 90° substantially around the rotor blade’s longitudinal direction, displacing said rotor blade’s and the hook arrangement’s position relative to the tower, when the rotor blade’s longitudinal direction is arranged in a substantially vertical direction.

[0034] After the hook arrangement is attached to the rotor blade, the rotor blade may be rotated in a rotated angled position between + / - 90° relative to the initial position, when the rotor blade’s longitudinal direction is arranged in a substantially vertical direction. This also applies for other component types, than the rotor blade. If the rotor blade is released from the hub, the initial position may be similar to the arranged position in the hub, and if arranged so, in a vertical displaced position.

[0035] If the rotor blade is arranged on the ground, the initial position may relate to being as when the rotor blade is lifted into a vertical position. When rotating the rotor blade around a vertical axis, the rotor blade’s and the hook arrangement’s position is displaced relative to the tower. The rotor blade may easily be rotated using the hook arrangement’s and if present one or more taglines. The rotor blade may be rotated, such that the ambient condition, e.g., the influence of wind etc. has a minimum impact on the rotor blade. The rotor blade may be rotated, such that the rotor blade is capable of being moved without damaging the tower or the rotor blade itself during hoisting.

[0036] In a still further method act of the invention, wherein:

[0037] - tilting said components first axis from a substantially vertical direction towards a horizontal direction around the combined center of gravity, keeping the combined center of gravity in the hoisting zone, or

[0038] - tilting said components first axis from a substantially horizontal direction towards the vertical direction around the combined center of gravity, such that the components first axis is arranged substantially along the tower of the wind turbine.

[0039] Replacing a component, for example a rotor blade, during maintenance is a complex task, due to the dimension and shape of the rotor blade, and the ambient conditions, such as wind impact and the location surroundings. The rotor blade may be released from the hub and arranged in a substantially vertical position. The rotor blade’s longitudinal direction from a substantially vertical direction may be tilted towards a horizontal direction around the combined center of gravity keeping the rotor blade in the hoisting zone. If the rotor blade is too close to the wind turbine tower, the combined center of gravity may be displaced, e.g., by rotating the rotor blade. The nacelle may yaw into the second nacelle yaw position, while keeping the crane boom in the first crane yaw position relative to the hub end. If present, the tagline or taglines may hold the rotor blade, such that the rotor blade may be tilted towards a substantially horizontal direction, when the nacelle may be yawed the second nacelle yaw position. The rotor blade may be tilted without being placed in the hazardous situation of hitting the wind turbine tower. If the combined center of gravity of the combined load has not been displaced relative to the wind turbine tower, the root of the rotor blade may hit and damage the wind turbine tower. The rotor blade may then safely be lowered down to the foot of the wind turbine tower.

[0040] The rotor blade may be resting on the ground at the foot of the wind turbine tower, ready for replacing an existing rotor blade. The rotor blade may first be lifted, such that the elongated rotor blade may be capable of being tilted from a substantially horizontal direction towards a substantially vertical direction around the combined center of gravity, such that a root of the rotor blade may face the hub end of the nacelle having a longitudinal axis arranged substantially along the tower of the wind turbine. If needed, the rotor blade may be rotated, such that hub easily may receive the root of the rotor blade. Instead of the up-tower crane may use the crane yaw system, the yaw movement may be provided by the nacelle yaw system.

[0041] In a further method act of the invention of yawing the nacelle in a yaw angle between + / - 90° relative to the nacelle’s hub end during hoisting operation.

[0042] The wind turbine may be placed in a parked position when the wind turbine needs to be inspected or maintained. The wind turbine may be parked, such that the hub is arranged up against the wind. When yawing the nacelle, the nacelle may be moved away from the upcoming wind direction. Then wind may be an important factor when replacing rotor blades, and at the same time yawing the nacelle into a hoisting position. The nacelle may be parked in parked position, which may be defined as 0° relative to the nacelle’s hub end. The nacelle may be yawed in the nacelle in a yaw angle between + / - 90° during hoisting operation. Preferably, in a yaw angle between + / - 45°. More preferably, in a yaw angle between + / - 30°. Most preferably, in a yaw angle between + / - 20°.

[0043] In a further method of the invention, wherein the method comprise following act of hoisting said component within a working area, wherein said working area is located within a first circle having a radius 100% a rotor blade length from the wind turbine tower.

[0044] A first circle may be defined, wherein the first circle may have a first radius from the tower of the wind turbine or from the center of the tower of the wind turbine. The working area may be located within the first circle, such that all components are being handled close to the tower. As the wind turbines are getting larger, the required working area may also be larger. The complication may be that the surroundings of the wind turbine location may be more or less impassable, and therefore not suitable for provided a large working area. Large components, such as rotor blade, and supporting equipment may be difficult to handle, if the rotor blade may be handled using taglines for guiding away from the wind turbine.

[0045] The up-tower crane is capable of hoisting the component, e.g., a rotor blade, along the wind turbine tower, within a working area near to the wind turbine tower. The working area may be within the first circle radius of 100% a rotor blade length from the wind turbine tower. Preferably, within a radius of 90%. More preferably, within a radius of 80%. Most preferably, within a radius of 75%. The working area may located within a predetermined sector of the first circle. The predetermined sector of the first circle may be within + / - 90° with reference to the first crane yaw position or to the first nacelle yaw position.

[0046] In a further method of the invention, wherein the method comprise following act of arranging at least one winch system comprising one or more taglines within a second circle having a radius of 100% of a tower height from the tower.

[0047] One or more taglines may be used for guiding the components during hoisting. The winch system or winch systems may be arranged in a narrow distance to the wind turbine tower. A second circle may be determined and may have a second radius from the tower of the wind turbine or from the center of the tower of the wind turbine. The winch systems may be located within the second circle. The winch systems are using the taglines, such that the winch system or winch systems are still capable of guiding or supporting the component within the working area. The winch systems are using the taglines, such that when rotating, tilting and / or hoisting the component, the component avoids collision with the wind turbine tower.

[0048] In a further method act of the invention, wherein hoisting zone is within a yawing angle of the crane boom between 60° and 140° relative to a center line of said load rating chart.

[0049] The up-tower crane may work only in a predetermined yawing angle relative to the nacelle hub end. The up-tower crane’s crane boom may work in a hosting zone selected within a yawing angle span of the crane boom between 60° and 140° according to the load rating chart’s 0° center line. The center line may be perpendicular to the longitudinal direction of the nacelle. Preferably, a yawing angle span between 80° and 120°. More preferable a yawing angle span between 90°-l 10°. Viewing a load rating chart related to the up-tower crane in cooperation with a wind turbine, the hoisting zone in front of the nacelle hub end provides the highest lifting capacity. When the up-tower crane works in the preferred hoisting zone, the up-tower crane’s size may be kept at a minimum, even though the wind turbine is getting larger. The up-tower crane may therefore provide the adequate lifting capacity needed for the hoisting tasks required, when cooperating with the wind turbine.

[0050] The hoisting system optimizes the hoisting performance when the hoisting system uses the benefit of cooperating with the wind turbine. Using the wind turbine’s yaw system to keep the up-tower crane’s crane boom in a substantially constant position relative to the hub end, wherein the lifting capacity is at the highest. The hoisting system as being in cooperation with the wind turbine is capable of handling large and heavy components in an agile and safe manner, which reduces the need for larger up-tower cranes and larger working areas. This reduces the operation complexity, time consumption and costs of hoisting before, during and after the hoisting procedure.

[0051] The total weight the up-tower crane is able to lift safely based on load radius may also be taken into consideration. The total weight comprises the weight of the main wire, the hook arrangement and the component to be hoisted. The up-tower crane may preferably hoist a larger weight when booming the crane boom into a substantially vertical position, compared to booming the crane boom into a substantially horizontal position. When the crane boom is booming to the substantially horizontal position it is preferred that the wires may be as short as possible, such that the total weight carried by the up-tower crane is mainly the weight of the hook arrangement and the component to be hoisted. When the crane boom is booming to the substantially vertical position, the wires may have a length used for hoisting purpose wherein the total weight carried by the up-tower crane is the total weight of the main wire, hook arrangement and the component to be hoisted.

[0052] This invention has now been explained with reference to a few embodiments and methods, which have only been discussed to illustrate the many varying possibilities achievable with the method according to the present invention.

[0053] Brief description of the drawings

[0054] The embodiments of the invention are described in the following with reference to:

[0055] Fig. la,b: Illustrating an up-tower crane having a crane boom in a first and a second booming position.

[0056] Fig. 2a, b: Illustrating a load rating chart of an up-tower crane when attached to a nacelle on a wind turbine.

[0057] Fig. 3a, b: Illustrating an up-tower crane preparing a detachment of a rotor blade from a hub.

[0058] Fig. 4a,b,c: Illustrating an optimizing hoisting performance of a wind turbine hoisting system, when detaching a rotor blade.

[0059] In the explanations of the figures, identical or corresponding components will be provided with the same designations in different figures. Therefore, no explanation of all details will be given in connection with each single figure / embodi- ment.

[0060] Detailed description

[0061] Embodiments of the invention are explained in the following detailed description. It is to be understood that the invention is not limited in its scope to the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways.

[0062] Fig. la,b illustrates an up-tower crane 1 having crane base part 2 and a crane boom 3 in a first booming position, illustrated in fig. la, and a second booming position, illustrated in fig. lb. The up-tower crane 1 is configured to be attached to a nacelle on a wind turbine. The up-tower crane comprises furthermore a main wire, not visible in the fig. la,b, having a hook arrangement 4. The up-tower crane 1 is configured to hoist a component within a predefined hoisting zone in cooperation with the wind turbine. When the up-tower crane 1 may be arranged in the first booming position as in fig. la, the crane boom 3 may be arranged substantially horizontal position, which in this example may be approximately 13,7° displaced relative to a horizontal axis. The first booming position may provide a first lifting capacity. When the up- tower crane 1 is arranged in the second booming position as in fig. lb, the crane boom 3 is arranged substantially vertical position relative to a vertical axis, in this example having a hight of 8600 mm from the base bottom to a hook arrangement 4. The second booming position may provide a second lifting capacity different from the first lifting capacity. The first booming position, illustrated in fig. la, and a second booming position, illustrated in fig. lb, are the two outer booming positions, which the up-tower crane 1 is capable of booming within. Beside booming the crane boom 3, the up-tower crane 1 comprises a yaw system, such that the crane 1 is capable of yawing relative to the nacelle.

[0063] Fig. 2a, b illustrates a load rating chart of an up-tower crane 1 when attached to a nacelle on a wind turbine. The dotted lines illustrate the load rating chart relative to the nacelle 8 and hub 9, based on the up-tower crane’s 1 mounting position on or in the nacelle 8. The up-tower crane’s 1 yaw system may be configured to yaw the up- tower crane 1 + / - 160° relative to a center line C at 0°.

[0064] The hoisting zones 5,10,30,31,50,51, provide different lifting capacities, and may be determined from the load rating chart, which may be related to a specific type of up-tower crane mounted on a specific type of wind turbine. Showed in table in fig. 2b. The outer circle 1 ' is illustrating the up-tower crane 1 having the crane boom 3 in the first booming position as shown in fig. la. The inner circle 1" is illustrating the up-tower crane 1 having the crane boom 3 in the second booming position as shown in fig. lb. Between the outer circle 1 ' and the inner circle 1" are defined the hoisting zones, wherein the hoisting zones 5,10,30,31,50,51 provides different lifting capacity relative to the up-tower crane’s 1 crane yaw position and the booming position of the crane boom 3.

[0065] Between the outer circle 1 ' and the inner circle 1" are a plurality of hoisting zones 5,10,30,31,50,51 defined, for example an ad hoc hoisting zone 5, where in the table in fig. 2b shows that the maximum lifting capacity in hoisting zone 5 is 10.000 kg, when the up-tower crane 1 has a yaw angle between -160° to 160° between the first and the second booming position having a booming angle between 13.7° and 93.4°. The table in fig. 2b also shows that the maximum lifting capacity in hosting zone 10 is 47,040 kg, when the up-tower crane 1 has a yaw angle between 96° and 106° and the booming position has a booming angle between 58.7° and 93.4°. The table in fig. 2b furthermore shows that the maximum lifting capacity in hosting zone 31 is 34,000 kg, when the up-tower crane 1 has a yaw angle between 91° and 101° and the booming position has a booming angle between 15.6° and 93.4°.

[0066] The load rating chart clearly shows that the highest lifting capacity is achieved at the nacelle’s 8 hub end and hub 9, in the hoisting zones 10 and 31. The lifting capacity clearly decreases much when entering the hoisting zone 5 next to the hoisting zones 10 and 31. It is therefore clearly preferred to operate in the hoisting zones 10 and 31. The alternative is to provide larger up-tower cranes 1 as the wind turbines 11 are getting larger. If operating in the in the hoisting zones 10 and 31, a smaller and cheaper up-tower crane 1 may be chosen.

[0067] Fig. 3a, b illustrates an up-tower crane preparing a detachment of a rotor blade

[0068] 13 from a hub 9. The wind turbine 11 comprises a tower 12 and a nacelle 8 with a hub 9. The hoisting system comprises an up-tower crane 1 arranged in or on the nacelle 8 behind the hub 9. The up-tower crane 1 is configured to yaw into at least one crane yaw position, illustrated with the arrow A1. The up-tower crane 1 is configured to hoist a component, in this example a rotor blade 13 having a first axis which is the longitudinal axis of the rotor blade 13. The rotor blade 13 is positioned in a first loading position still attached to the hub 9, wherein the rotor blade 13 is arranged in a substantially vertical direction. The up-tower crane 1 and the wind turbine 11 in cooperation defines a load rating chart having a plurality of hoisting zones as described in fig. la,b and fig. 2a, b. The up-tower crane 1 comprises a crane boom 3 and a main wire, not visible in fig. 3a, b, and a hook arrangement 14,15,16 comprising a carry arrangement 16 having an upper carry part 161connected to a lower carry part 162. The carry arrangement 16 may be arranged between the main wire and the yoke device 14,15. The yoke device 14 may be clamped to the rotor blade 131in a first blade position and a tagline device 15 arranged in a distance connected by a wire, attached to the rotor blade 131in a second blade position. One or more taglines 18 are connected to the tagline device 15.

[0069] Fig. 4a,b,c illustrates an optimizing hoisting performance of a wind turbine hoisting system, when detaching a rotor blade 131. The wind turbine 11 is secured, all the systems, including the yaw system, not shown in fig. 4a,b,c, are in a parked idle mode and ready for maintenance. Instead of the up-tower crane 1 may use the crane yaw system, the yaw movement may be provided by the nacelle yaw system, such that the up-tower crane 1 continuously is working in the optimal hoisting zone 5,10,30,31,50,51.

[0070] Fig. 4a illustrates the wind turbine in a parked position pointing the hub up against the wind illustrated by the dotted line by the arrow W. The wind turbine will be parked up against the wind, having a first nacelle yaw position P1. In this example the present replaceable rotor blade 131is being replaced with a new replacement rotor blade 132. The load position of the present replaceable rotor blade 13 is arranged relative to the hub. The load position of the new replacement rotor blade 132is on the ground in an angled position to the first nacelle yaw position P1close to the wind turbine tower. A first circle 01has a first radius to the tower of the wind turbine 11. The working area is located within the first circle 01. A second circle 02has a second radius to the tower of the wind turbine 11. The winch systems 17 are located within the second circle 02. The winch systems 17 comprises taglines 18 which is connected to the hoisting arrangement 14,15,16.

[0071] The up-tower crane 1 is then yawed to a first crane yaw position, such that the crane boom 3 extends in a boom direction of the nacelle’s hub 9. The first crane yaw position may be aligned with the first nacelle yaw position P1. The nacelle’s 8 yaw system is activated for hoisting use, and nacelle’s 8 is yawed into a second nacelle yaw position P2different than the first nacelle yaw position P1, within a first yaw angle -cp1, while keeping the up-tower crane 1 in the first crane yaw position relative to the hub 9. The hoisting arrangement 14,15,16 is attached to the rotor blade 13, as illustrated in fig. 3a, b. The taglines 18 are connected to the hoisting arrangement. The nacelle 8 may stay in the second nacelle yaw position P2, while the rotor blade 131may be released from the hub.

[0072] Knowing the nacelle’s 8 first nacelle yaw position, the up-tower crane 1 is capable of being yawed to the predetermined first crane yaw position relative to the nacelles first nacelle yaw position P1. The up-tower crane 1 may mostly be operated within the hoisting zones 5,10,30,31,50,51, which provides the highest lifting capacity. The up-tower crane 1 may have a minor working space degree, which deviates from the optimal position, if needed. While hoisting the rotor blade 131from the first load position, for example at the hub 9, to a second load position, for example resting pads 19 on the ground level, the up-tower crane 1 is arranged, such that the up-tower crane 1 has an optimal high lifting capacity.

[0073] Fig. 4b illustrates the nacelle 8 yawed a second yaw angle cp2to the third nacelle yaw position P3different from the second nacelle yaw position P2, still keeping the up-tower crane 1 in the first crane yaw position relative to the hub 9. The rotor blade 131may alternatively be released from the hub 9, while the nacelle 8 is arranged in the third nacelle yaw position P3The rotor blade 131is arranged in a vertical position substantially along the wind turbine tower 12, as illustrated in fig. 3a, b. After the hook arrangement 14,15,16 is attached to the rotor blade 131, the rotor blade 131may be rotated in a rotated angled position between + / - 90° relative to the vertical position, along the rotor blade’s 131longitudinal direction. When rotating the rotor blade 131substantially around the rotor blade’s 131longitudinal axis, the rotor blade’s 131and the hook arrangement’s 14,15,16 position may be displaced relative to the wind turbine tower. The taglines 18 from the winch systems 17 may be attached as described in fig. 3a. The rotor blade’s 131and the hook arrangements’ 14,15,16 combined center of gravity may be adjusted to prepare the tilting, or during tilting of the rotor blade 131into a substantial horizontal position. The rotor blade’s 131and the hook arrangement’s 14,15,16 combined center of gravity may be adjusted or the position may be altered to avoid damage the wind turbine tower 12 during hoisting. The rotor blade 131may easily be rotated using the hook arrangement 14,15,16 and if present one or more taglines 18. The rotor blade 131may be rotated relative to the wind direction W, such that the ambient condition, e.g., the influence of wind etc. has a minimum impact on the rotor blade 13 h

[0074] Fig. 4c illustrates the nacelle 8 arranged in the third nacelle yaw position P3. The rotor blade 131has been released from the hub 9 and arranged in a substantially vertical position as described in fig. 4a, b. The rotor blade’s 131longitudinal direction may be tilted from a substantially vertical direction towards a substantially horizontal direction around the combined center of gravity, keeping the rotor blade 131in the working area. The nacelle 8 may be yawed into the third nacelle yaw position P3, while keeping the crane boom 3 in the first crane yaw position relative to the hub end of the nacelle 8, such that the rotor blade 131is tilted towards a substantially horizontal position, without being placed in the hazardous situation of hitting the wind turbine tower 12 during tilting. The length of the taglines 18 is adjusted, such that the taglines 18 move the rotor blade 131into a position, where the rotor blade 131is tilted towards a substantially horizontal direction, when the nacelle 8 in this example is being yawed in to the third nacelle yaw position P3. The rotor blade 131may be tilted without being placed in the hazardous situation of hitting the wind turbine tower 12.

[0075] If the rotor blade 131is too close to the wind turbine tower, rotor blade 131longitudinal axis may be yawed around the combined center of gravity when being in a substantially horizontal position, e.g., by rotating the rotor blade 13, for example by the support of the taglines 18, illustrated by the arrows. The rotor blade 131may then safely be lowered down to the foot of the wind turbine tower 12. If the rotor blade 13 is a new replacement rotor blade 132and the rotor blade 132is resting on the ground at the foot of the wind turbine tower 12, the rotor blade may first be lifted in a horizontal position. The replacement rotor blade 132is capable of being tilted from a substantially horizontal direction towards a substantially verti- cal direction around the combined center of gravity, such that a root of the rotor blade 132is facing the hub end of the nacelle 8. After the rotor blade 132longitudinal axis has been arranged in a vertical position may be rotated, such that hub 9 easily may receive the root of the rotor blade 132.

Claims

PATENT CLAIMS1. A method for optimizing hoisting performance of a wind turbine hoisting system, wherein said wind turbine (11) comprises a tower (12) and a nacelle (8) having a hub (9) end, wherein said hoisting system comprises an up-tower crane (1) arranged in or on the nacelle (8), wherein the up-tower crane (1) and the wind turbine in cooperation defines a load rating chart having a plurality of hoisting zones (5,10,30,31,50,51), wherein said up-tower crane (1) comprises a crane boom (3) and a main wire, wherein the up-tower crane (1) is configured to yaw into at least one crane yaw position, wherein the main wire having a hook arrangement (4,14,15,16), wherein the up-tower crane (1) is configured to hoist a component (13) according to said load rating chart, wherein the component (13) has a first axis, wherein the method comprises the following acts of: selecting at least one of said plurality of hoisting zones (5,10,30,31,50,51), determining a first nacelle yaw position (P1) of the said nacelle (9), determining a first load position of said component (13),- yawing said up-tower crane (1) to a first crane yaw position, such that said crane boom (3) extends in a boom direction of the nacelle’s (8) hub (9) end within a predetermined hoisting zone (5,10,30,31,50,51), wherein the crane boom (3) is arranged in a first booming position,- yawing said nacelle (8) into a second nacelle yaw position (P2) different than said first nacelle yaw position (P1), while keeping the up-tower crane (1) in said first crane yaw position relative to the hub (9) end, hoisting said component (13) from said first load position to a second load position.

2. Method according to claim 1, wherein the method comprises one or both of further acts:- yawing the nacelle (8) to a third nacelle yaw position (P3) different from the second nacelle yaw position (P2),- moving the crane boom (3) to a second booming position different from the first booming position, while keeping said up-tower crane (1) in the first crane yaw position, such that crane boom (3) is arranged within in the predetermined hoisting zone (5,10,30,31,50,51).

3. Method according to claim 1 or 2, wherein the method comprises a further step of determining the crane boom’s (3) booming position relative to the length of the main wire, when hoisting said component (13) from said first load position to said second load position.

4. Method according to claim 1, 2 or 3, wherein the method comprises one or more of further acts: determining one or more nacelle yaw positions (P1, P2, P3) from at least one ambient condition acting on the component (13), determining the crane boom’s (3) booming position from at least one ambient condition acting on the component (13).

5. Method according to any one of the preceding claims, wherein the method comprises the following act of arranging the component (13) in a rotated angled position between + / - 90° substantially around a first axis of the component’s (13) during hoisting operation, displacing said component’s (13) and the hook arrangement’s (4,14,15,16) position relative to the tower (12), when the first axis of the component (13) is arranged in a substantially vertical direction.

6. Method according to any one of the preceding claims, wherein the method comprises one of the following acts:- tilting said components (13) first axis from a substantially vertical direction towards a horizontal direction around the combined center of gravity, keeping the combined center of gravity in the hoisting zone (5,10,30,31,50,51), or- tilting said components (13) first axis from a substantially horizontal direction towards the vertical direction around the combined center of gravity, such that the components (13) first axis is arranged substantially along the tower (12) of the wind turbine (11).

7. Method according to any one of the preceding claims, wherein the method comprises the following acts of yawing the nacelle (8) in a yaw angle between + / - 90° relative to the nacelle’s (8) hub (9) end during hoisting operation.

8. Method according to any one of the preceding claims, wherein the method comprises the further act of- hoisting said component (13) within a working area, wherein said working area is located within a first circle (01) having a radius of 100% a rotor blade (13) length from the wind turbine tower (12).

9. Method according to any one of the preceding claims, wherein the method comprises the further act of- arranging at least one winch system (17) comprising one or more taglines (18) within a second circle (02) having a radius of 100% of a tower height from the wind turbine tower (12).

10. Method according to any one of the preceding claims, wherein hoisting zone (5,10,30,31,50,51), is within a yawing angle of the crane boom (3) between 60° and 140° relative to a center line (C) of said load rating chart.

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