Method and apparatus of performing maintenance on a wind turbine component

A method of performing maintenance on a wind turbine component (18, 22, 24) of a wind turbine (10) having an integrated lifting apparatus (40). The method includes lifting a first temporary support (104) using the integrated lifting apparatus (40), coupling the first temporary support (104) to the nacelle (12) or the hub (16) and the integrated lifting apparatus (40), removing the wind turbine component (18, 22, 24) using the integrated lifting apparatus (40) and the first temporary support (104) in combination. The method may further include installing a replacement wind turbine component (18, 22, 24) using at least a part of the integrated lifting apparatus (40) and the first temporary support (104) in combination, decoupling the first temporary support (104) from the nacelle (12) or the hub (16) and the integrated lifting apparatus (40), and removing the first temporary support (104) from the wind turbine (10) using the integrated lifting apparatus (40). A system for performing maintenance on a wind turbine component (18, 22, 24) is also disclosed.

TECHNICAL FIELD

The invention relates to a method and apparatus of performing maintenance on a wind turbine component, particularly using at least one temporary support in combination with an integrated lifting apparatus.

BACKGROUND

Large, utility-scale horizontal-axis wind turbine generators (HAWTs) typically include a plurality of rotor blades mounted to a supporting structure, usually in the form of a tubular tower. In such HAWTs, the generating components, including the generator, gearbox, drive train and brake assembly, are located at the top of a tower in a nacelle behind the hub of the rotor blades.

Maintenance of wind turbine components within the nacelle may be performed by personnel having access to the interior of the nacelle. For example, a suitable ladder system may be located within the tower so that personnel can climb to the top of the tower. Alternative access options are for personnel to be flown to the wind turbine generator by helicopter and winched zo onto the nacelle for personnel to be conveyed to the nacelle by a ‘cherry picker platform’ provided by a ground-based crane for an on-shore wind turbine.

Further, it is generally known to install an integrated lifting apparatus within the nacelle in order to help personnel repair and/or replace various components. For example, WO2012/107049 describes an internal lifting apparatus that is mounted within the nacelle of a HAWT, where the boom of the integrated lifting apparatus is movable in elevation and in azimuth in relation to the nacelle. Additionally, WO2015/078475 describes that the frame structure of the nacelle may include a support structure against which a crane may be brought to rest in a stowed condition to prevent damage caused by oscillations when the wind turbine is in use.

While the integrated lifting apparatus is suitable for replacing smaller wind turbine components, certain large wind turbine components often exceed the lifting capacity of the internal lifting apparatus. These large wind turbine components may include the gearbox and the generator. For example, the typical lifting capacity of the internal lifting apparatus is only about 3 tons, while the generator weighs about 30 tons and the gearbox weighs about 70 tons. Since the weight of either of these large wind turbine components exceeds the lifting capacity of the integrated lifting apparatus, special equipment must be introduced to replace these components. Even though the probability of large wind turbine component failure is low, the associated cost of repairing and/or replacing the large wind turbine component is significant.

Two options are currently employed for replacing large wind turbine components in the wind turbine. First, regarding off-shore wind turbines, a jack-up vessel containing a large independent crane is generally used. The jack-up vessel contains the necessary crane components to remove and replace the large wind turbine component without using the integrated lifting apparatus. Since jack-up vessels are able to replace large wind turbine components, jack-up vessels are generally very large and expensive to operate. In addition to the significant cost associated with utilizing the jack-up vessel, since failure events are unexpected, unplanned downtime caused by such a failure is also very costly. On-shore wind turbines also use large land-based cranes that are also expensive to transport to a wind turbine site and operate. Alternatively, if the integrated lifting apparatus of the wind turbine is made in such a manner as to allow for the large wind turbine components to be removed and replaced merely by using the integrated lifting apparatus, the additional weight and cost of such a structure would make this option also undesirable.

Accordingly, there is a need for an improved method of performing maintenance on a wind turbine component, where the weight of the large wind turbine component to be removed exceeds the capacity of the integrated lifting apparatus, without the need for heavy permanent modifications to the integrated lifting apparatus or using expensive jack-up vessels and cranes.

SUMMARY

A method of performing maintenance on a wind turbine component of a wind turbine is disclosed. The wine turbine includes a tower, a nacelle, a hub, and at least one rotor blade. The wind turbine further includes an integrated lifting apparatus. The method comprises lifting a first temporary support using at least part of the integrated lifting apparatus of the wind turbine and coupling a first end of the first temporary support to the nacelle or the hub and a second end of the first temporary support to the integrated lifting apparatus. The wind turbine component may then be removed using at least part of the integrated lifting apparatus and the first temporary support in combination. A replacement wind turbine component may then be installed using at least part of the integrated lifting apparatus and the first temporary support in combination. The method further includes decoupling the first end of the first temporary support from the nacelle or the hub and the second end of the first temporary support from the integrated lifting apparatus and removing the first temporary support from the wind turbine using the integrated lifting apparatus.

In one embodiment, the nacelle includes a frame structure and the first end of the first temporary support includes first and second legs and coupling the first end of the first temporary support further includes coupling the first leg to a first side of the frame structure and coupling the second leg to a second side of the frame structure. Additionally, decoupling the first end of the first temporary support further includes decoupling the first leg from the first side of the frame structure and the second leg from the second side of the frame structure. The first side of the frame structure may include first side upper and lower horizontal members and first side bridging members extending therebetween. The second side of the frame structure may include second side zo upper and lower horizontal members and second side bridging members extending therebetween. The method further includes coupling the first leg to the first side upper horizontal member, the first side lower horizontal member, and/or at least one of the first side bridging members; and coupling the second leg to the second side upper horizontal member, the second side lower horizontal member, and/or at least one of the second side bridging members.

In the various embodiments, the wind turbine component being removed has a weight that exceeds the lifting capacity of the integrated lifting apparatus alone, but does not exceed the lifting capacity of the integrated lifting apparatus and the first temporary support when used in combination. By way of example, the method may include removing a generator or a gearbox from the wind turbine, both of which may exceed the capacity of the integrated lifting apparatus alone, but not the combination of the integrated lifting apparatus and the first temporary support.

In one embodiment, the wind turbine component being removed is in the nacelle. In this case, the method may include lifting the first temporary support into the nacelle through one or more closeable doors located on a top portion of the nacelle. Moreover, the method may further include removing the wind turbine component down through a hatch located on a bottom portion of the nacelle. The step of installing the replacement wind turbine component may then include inserting the replacement wind turbine component up through the hatch in the bottom portion of the nacelle.

In another embodiment, the wind turbine component being replaced is a rotor blade. In this regard, the method further includes lifting a second temporary support using the integrated lifting apparatus and coupling the second temporary support to the nacelle, such as the frame structure. The method further includes removing the rotor blade using at least part of the integrated lifting apparatus, the first temporary support, and the second temporary support in combination. In this embodiment, the integrated lifting apparatus may include an extendible boom, one or more winches, first and second pulley systems, and first and second lifting lines. Removing the rotor blade further includes aligning the first temporary support to the center of gravity of the rotor blade; disconnecting the rotor blade from the hub; lowering the rotor blade using the first and second lifting lines, the first and second pulley systems, and one or more winches, the integrated lifting apparatus and the first zo temporary support in combination; and rotating the rotor blade to be generally perpendicular to the tower. In this regard, the first lifting line, the first pulley system, the integrated lifting apparatus and the first temporary support in combination support a first portion of the rotor blade, and the second temporary support, the second pulley system, and the second lifting line support a second portion of the blade.

DETAILED DESCRIPTION

FIG. 1shows a schematic view of a wind turbine10of the horizontal-axis type (HAWT) as including a nacelle12mounted on top of a tower14, with the tower14being mounted on a foundation or footing. The nacelle12includes a hub16at its front end that carries a plurality of rotor blades18. Three rotor blades18are shown in this embodiment, as is common with large utility-scale generators, however, persons skilled in the art would appreciate that other numbers of rotor blades18may also be suitable. Moreover, other tower constructions are also envisioned, for example, a tower14defined by a structural lattice framework.

Although many of the individual components are not shown in the figures for clarity, the nacelle shown inFIG. 1includes a generator set20(including a gearbox22and a generator24), a low speed drive shaft26, and a high speed output shaft28(all of which are shown using dashed lines). The generator set20enables energy to be recovered from the rotor blades18, and is driven by the hub16through the low speed drive shaft26. The generator set20is typical of a HAWT with the gearbox22stepping up the rotational speed of the low speed drive shaft26to the high speed output shaft28that ultimately drives the generator24. The generator24outputs alternating current (AC) at a voltage and frequency that is determined largely by the rotational speed of the hub16. The functional components of the nacelle12may be mounted to at least one of the frame structure30of the nacelle12, the main shaft bearing zo housing32, and/or the gearbox22.

To enable variable speed operation of the wind turbine10, the alternating current output by the generator24is first converted, or ‘rectified’, to direct current (DC) and is then converted back into alternating current, or ‘inverted’, at the correct frequency and voltage in order to integrate with the frequency and voltage that is required from the national grid system via supply line (not shown). The process of rectification and inversion is handled by a power system34that is contained in an internal tower structure36to which the generator24is electrically connected by way of a high voltage AC current line38.

Having described the overall structure of the wind turbine10, discussion will now turn to the integrated lifting apparatus40that is located within the nacelle12, as shown inFIGS. 2 and 3. According to an exemplary embodiment, the integrated lifting apparatus40may be in the form of a cantilevered telescopic boom crane that includes a base42fixed to the nacelle12and a boom44that is articulated on and cantilevered from the base42. As shown inFIG. 2, and more clearly in the schematic representations ofFIGS. 5 and 6, the base42of the integrated lifting apparatus40is mounted to a main shaft bearing housing32of the nacelle12. Additionally, persons skilled in the art would appreciate that although the integrated lifting apparatus40is shown as being located within the nacelle12, the integrated lifting apparatus40may also be located at other locations, for example, within the tower14.

The integrated lifting apparatus40may have three degrees of freedom (telescope, elevate, and slew) allowing for access to many areas of the nacelle12. For this reason, the integrated lifting apparatus40includes a power system (not shown), which is configured to drive the telescopic, elevation and slewing (i.e. azimuth) operations of the boom44relative to the base42. In one exemplary embodiment, the power system may be an electrohydraulic power system. In the deployed condition, the boom44may be extended telescopically so as to reach a maintenance platform46shown inFIG. 2that is mounted to the rear of the upper deck48of the nacelle12.

The integrated lifting apparatus40is configured to be placed in two conditions or modes: i) a first ‘stowed’ condition in which the boom44is housed within the nacelle12and ii) a second ‘deployed’ condition in which the boom44is movable with respect to the base42of the integrated lifting zo apparatus40. As shown in ‘stowed’ condition ofFIG. 3, the integrated lifting apparatus40is fixedly mounted to the main shaft bearing housing32, such that the boom44extends in the longitudinal direction ‘L’ along a centerline of the nacelle12and is surrounded by the frame structure30. When the integrated lifting apparatus40is placed in the deployed condition (shown inFIG. 2), the boom44is operable to extend out from the confines of the nacelle12to reach above the first and second closable doors50a,50bthat define a roof of the nacelle12(when first and second closable doors50a,50bare closed). In the deployed condition, the boom44is operable to extend in telescopic, elevation and slewing. For example,FIGS. 2 and 4A-8Cshow where the boom44extends beyond an upper deck48of the nacelle12. In this deployed condition, the boom44may be swung out beyond the side of the nacelle12to hoist payloads from ground level up to the nacelle12.

As shown inFIG. 2, and more clearly inFIGS. 5 and 6, a first winch52may be provided near a base end56of the boom44that spools out a first lifting line54. The first winch52may be a temporary high power winch that is lifted by the integrated lifting apparatus40up to the nacelle12. Alternatively, while not shown, the first winch52may be located near the base of the wind turbine10, located on a nearby vessel (for off-shore wind turbines), or located near the ground (for on-shore wind turbines). According to an exemplary embodiment, the first lifting line54may be in the form of a steel cable that is routed through a suspension point at a free end58of the boom44to terminate in a first lifting attachment60, such as a hook. However, persons skilled in the art would appreciate that a variety of winches, lifting lines, and lifting attachments may be suitably utilized. It should be appreciated that the integrated lifting apparatus may include both permanent components (such as the extendible boom) and temporary components (such as different winches, and pulleys) that are operatively coupled to permanent aspects of the apparatus for replacing the wind turbine component, which results in using at least part of the integrated lifting apparatus. Using at least part of the integrated lifting apparatus may include using the extendible boom and one or more winches (permanent or temporary), and/or one or more or pulley systems (as will be described in relation toFIGS. 8A-C). For example, the original on-board winch installed on the integrated lifting apparatus may provide too little power, resulting in a larger and temporary first winch being used, possibly in addition to zo pulleys (not shown) being used both at the free end and near the first lifting attachment. Also, the diameter of the first lifting line (and the second lifting line for replacing the rotor blade shown inFIGS. 7A-8C) may be increased to adjust for the heavy load.

Having described the overall operation of the integrated lifting apparatus40in general terms, discussion will now turn to the more detailed construction of the frame structure30that provides the nacelle12with structural strength. As shown inFIG. 3, the frame structure30includes an outer sub-frame62that carries the outer skin64that defines the upper deck48and side walls66of the nacelle12. Typically, the outer skin64will be in the form of metal panels, for example steel or aluminum or a composite construction, for example, glass-fibre reinforced plastic (GRP). However, persons skilled in the art would appreciate the outer skin64may be formed from any suitable material. The outer sub-frame62includes a plurality of vertical members68or ‘stringers’ that are generally C-shaped in form. The outer sub-frame62provides a rib-type structure for supporting the outer skin64.

FIGS. 4A-4Cshow an exemplary frame structure30, however, it should be appreciated that the frame structure30may vary, and variations are not intended to fall outside the scope of the invention. As shown, frame structure30includes a first side70and a second side72. The first side70includes a first side upper horizontal member74, a first side lower horizontal member76, and first side bridging members78a-g(with78aand78bbeing hidden from view) extending therebetween. Similarly, the second side72includes a second side upper horizontal member80, a second side lower horizontal member82, and second side bridging members84a-gextending therebetween.

First and second upper front bridging members86,88separate the first side upper horizontal member74from the second side upper horizontal member80, while a first upper rear bridging member90separates the first side upper horizontal member74from the second side upper horizontal member80. Similarly, first and second upper rear bridging members94,96separate the first side upper horizontal member74from the second side upper horizontal members80, while a first lower rear bridging member98separates the first side zo lower horizontal member76from the second side lower horizontal member82. Connector elements102, such as gusset plates, may be included at some or all of the connection points of two or more members.

FIGS. 4A-4Dillustrate a method of performing maintenance on a wind turbine component, such as the generator24or the gearbox22of a wind turbine10, where the wind turbine component is located within the nacelle12. However, it should be appreciated that other wind turbine components may also be removed using this method. In particular,FIGS. 4A-4Dshow the process of replacing the generator24located within the nacelle12using a first temporary support104in combination with the integrated lifting apparatus40. For added clarity, many of the components of the wind turbine10have been removed entirely or shown using dashed lines, with only the frame structure30and its associated components, the integrated lifting apparatus40and its associated components, the generator24, and the first temporary support104being shown.

There are many benefits to using the first temporary support104in combination with the integrated lifting apparatus40to perform maintenance on a wind turbine component. First, no jack-up vessel is necessary when a large component is to be repaired and/or replaced. Generally, jack-up vessels cost far more than other vessels due to the capacity and size. Other vessels, such as dynamic positioning vessels, are sufficient to carry the first temporary support104in combination with the large wind turbine component. Additionally, the integrated lifting apparatus40does not need to be significantly modified and/or can be retrofitted if needed. This allows the exemplary method to be performed on wind turbines10already in use. Further, the first temporary support104provides a truss-like structure that lessens the tension and compression stress concentrations, allowing for the lifting capacity of the integrated lifting apparatus40to be greatly increased. Using the integrated lifting apparatus40alone creates a significant moment, the effect of which is greatly reduced using the first temporary support104.

While not shown, the first temporary support104may be brought to the wind turbine10using a variety of vehicles. For an off-shore wind turbine, the first temporary support104may be supplied to the wind turbine10by a helicopter or vessel, such as a dynamic positioning vessel. For an on-shore zo wind turbine, the first temporary support104may be supplied to the wind turbine10by a truck, train, or helicopter.

FIG. 4Ashows the integrated lifting apparatus40moving relative to the nacelle12to lift the first temporary support104. As shown, the first temporary support104may include a head portion106, a first leg108, a second leg110, and a body portion112therebetween. The head portion106may include first and second frame members114,116that may extend parallel each other and in a direction generally opposite the first and second legs108,110. The first and second frame members114,116may each include first receiving structures118,120that are configured to couple with a free end58of the integrated lifting apparatus40using a first connecting structure122(as shown inFIG. 4C). Preferably, the first temporary support104includes first and second legs108,110that allow the first temporary support104to attach to first and second sides70,72of the frame structure30. However, persons skilled in the art would appreciate that the first temporary support104may have various different shapes and sizes, that may depend on the frame structure30and/or integrated lifting apparatus40to which the first temporary support104connects with.

As shown, the first leg108includes a second receiving structure124configured to couple to the frame structure30(or the hub16as will be discussed below with respect toFIGS. 7A-8C) using a second connecting structure126. Similarly, the second leg110includes a third receiving structure128configured to couple to the frame structure30of the nacelle12using a third connecting structure130. As shown, the first and second legs108,110extend substantially parallel one another, however, this is not required. Additionally, the body portion112extends between the head portion106and the first and second legs108,110, and includes first and second oppositely angled frame members132,134attached on the ends by first and second cross members133,135. As shown, the first cross member133connects the head portion106, to the body portion112, while the second cross member135connects the first and second legs108,110to the body portion112.

The integrated lifting apparatus40may lift the first temporary support104through the bottom of the nacelle12through hatch136(shown inFIG. 6) or through the top of the nacelle12through the first and second closable doors50aand50b(shown inFIG. 3). One or more temporary support lifting lines138(such as lifting lines138a-d) may be attached to the first lifting attachment60.

FIG. 4Bshows the first and second legs108,110of the first temporary support104being coupled to the frame structure30. According to an exemplary embodiment, the first end140of the first leg108is coupled to the first side lower horizontal member76using a second connecting structure126. Similarly, the first end142of the second leg110is coupled to the second side lower horizontal member82using a third connecting structure130. While not shown, the first leg108may alternatively be coupled to the first side upper horizontal member74, and/or at least one of the first side bridging members78a-gor the main frame (not shown). Similarly, while not shown, the second leg110may be coupled to the second side upper horizontal member80and/or at least one of the second side bridging members84a-gor the main frame.

FIG. 4Cshows the second end144being coupled to a free end58of the integrated lifting apparatus40using a first connecting structure122. For example, the first connecting structure122, the second connecting structure126, and/or the third connecting structure130may be one or more dowel pins that allow the first temporary support104to pivot. Alternatively or in addition dowel pins, the first, second and third connecting structures122,126,130includes one or more bolts if rigidity is desired at the connection point.

FIG. 4Dshows wind turbine component being removed using the integrated lifting apparatus40and the first temporary support104in combination. The wind turbine component being removed has a weight that exceeds the lifting capacity of the integrated lifting apparatus40alone, but does not exceed the lifting capacity of the integrated lifting apparatus40and the first temporary support104when used in combination.

The schematic cross-sections ofFIGS. 5 and 6will now be discussed for greater clarity. As shown inFIG. 5, the first lifting line54may be extendable down inside the interior of the tower14. As shown inFIG. 6and similarly shown inFIG. 4D, the integrated lifting apparatus40may remove the first temporary support104from the wind turbine10using the first winch52and the first lifting line54through a hatch136located on a bottom portion146of the nacelle12. The reference position of first lifting line54may be above an aperture allowing the first lifting line54to extend down the outside of the tower14(as shown inFIG. 6). As shown, the nacelle12extends zo rearward from the tower14to define a significant overhang, with the bottom portion146of the overhang defining a hatch136, which may be permanently open or may use a closure device, such as a pivoted door148. The integrated lifting apparatus40is configured so that the free end58of the boom44is positioned over the hatch136. The first lifting attachment60at the end of the first lifting line54is therefore able to be extended down through the hatch136to lower items to the ground or to lift items to the nacelle12from the ground. The hatch136is provided in a location that is reachable by the integrated lifting apparatus40, for example through a rear wall150of the nacelle12, so that wind turbine components both large and small may be lifted and lowered outside of the tower14.

Inserting a replacement wind turbine component is performed using many of the same steps as described above, but in reverse. For example, the integrated lifting apparatus40and the first temporary support104are used in combination to insert the replacement wind turbine component through the hatch136located on the bottom portion146of the nacelle12or through the first and second closable doors50aand50bof the nacelle12.

Similar toFIG. 4B, the first end140of the first temporary support104may then be decoupled from the nacelle12. Accordingly, the first leg108may be decoupled from the first side lower horizontal member76and the second leg110may be decoupled from the second side lower horizontal member82. While not shown, the first leg108may alternatively be decoupled from the first side upper horizontal member74, and/or at least one of the first side bridging members78a-e.Similarly, the second leg110may be decoupled to the second side upper horizontal member80and/or at least one of the second side bridging members84a-e.

Similar toFIG. 4C, the first temporary support104may then be decoupled from the free end58of the integrated lifting apparatus40by removing the first connecting structure122. The first temporary support104is then removed from the wind turbine10using the integrated lifting apparatus40. Replacing the large wind turbine component in this exemplary manner, prevents the need for a jack-up vessel as described above, which saves both time and money. Additionally, using the first temporary support104in combination with the integrated lifting apparatus40greatly increases the lifting capacity of the zo integrated lifting apparatus40without significantly increasing its size and weight.

According to another exemplary embodiment shown inFIGS. 7A-8C, the wind turbine component being replaced is a rotor blade18. Discussion of this embodiment includes many of the same elements as the previously described embodiment, and these elements have been provided with similar reference numbers where the shown elements are substantially similar or identical. This exemplary embodiment utilizes the integrated lifting apparatus40in combination with both the first temporary support104and the second temporary support152, as will be discussed in greater detail below.

In this embodiment, the second temporary support152is lifted using the integrated lifting apparatus40in much the same manner as described above with respect to the first temporary support104. Likewise, the second temporary support152is coupled to the frame structure30in much the same manner as the first temporary support104, and will now be described in greater detail.

As shown inFIGS. 7A and 7B, the second temporary support152may include an attachment portion154and an outwardly extending portion156. However, persons skilled in the art would appreciate that the second temporary support152may have various different shapes and sizes. The attachment portion154may include a first attachment member158, a second attachment member160, and third attachment member162, which may each be attached to the frame structure30. As shown, the first end164of the first attachment member158may be attached to the first side upper horizontal member74using a fourth connecting structure170, the first end166of the second attachment member160may be attached to the first side upper horizontal member74using a fifth connecting structure172, and the first end168of the third attachment member162may be attached to the second side upper horizontal member80using a sixth connecting structure174.

Further as shown, the outwardly extending portion156may include a first outwardly extending member176, a second outwardly extending member178, and a third outwardly extending member180that may each terminate at a first end to create a second lifting location182outside of the nacelle12. The second end184of the first outwardly extending member176may be attached directly to the frame structure30, shown as the first side upper zo horizontal member74, or alternatively, may be attached to the first end164of the first attachment member158. Similarly, the second end186of the second outwardly extending member178may be directly attached to the frame structure30, shown as the first side upper horizontal member74, or alternatively, may be attached to the first end166of the second attachment member160. As shown inFIGS. 7A and 7B, the second end188of the third outwardly extending member180may be attached to the second ends190of the first, second, and third attachment members158,160,162at a rigid connection point.

After the second temporary support152is sufficiently coupled to the frame structure30of the nacelle12, the integrated lifting apparatus40may be completely disconnected from the second temporary support152, so that the integrated lifting apparatus40may lift the first temporary support104. Once lifted, the first temporary support104is coupled to hub16shown inFIGS. 7A and 7B(using dashed lines). According to an exemplary embodiment, the first leg108of the first temporary support104may be coupled to a first attachment location192of the hub16and the second leg110of the first temporary support104may be coupled to a second attachment location194of the hub16.

Similar to above, the integrated lifting apparatus40may include a system of winches, pulleys, lifting lines, and lifting attachments. For example, as shown, the integrated lifting apparatus40may include the first winch52, the second winch (not shown), the first and second pulley system195,196, first and second lifting lines,54,198, a first lifting attachment60and a second lifting attachment (not shown). As previously discussed, the first and second winches, first and second pulley systems195,196and first and/or second lifting lines54,198may be temporary resulting in using only part of the integrated lifting apparatus40. As most clearly shown inFIGS. 7A and 7B, one or more flexible supports199a,199bmay help to support the rotor blade18while it is being removed. As shown, a portion of the first lifting line54is placed between the rotor blade18and the flexible supports199a,199bfor increased control and support.

FIG. 7Bshows the rotor blade18being disconnected from the hub16using the integrated lifting apparatus40in combination with the first temporary support104, and the second temporary support152. As shown, the attachment structure connecting the rotor blade18to the hub16have been removed allowing the flange200of the rotor blade18to be separated from the hub16.

In removing the rotor blade18, special attention is given to the center of gravity (CG) of the rotor blade18as will now be discussed with respect toFIGS. 8A-8C.FIGS. 8A-8Cshow schematic illustrations of the rotor blade18being removed and lowered. The first temporary support104is aligned to the center of gravity of the rotor blade18. As shown inFIG. 8A, the rotor blade18is lowered using the first lifting line54, the first winch52, the integrated lifting apparatus40and the first temporary support104in combination. The second lifting line198may be free or taut and may be removably connected to the rotor blade18using a sleeve, for example in the form of a sack or sling, that is fitted over the tip of the rotor blade18when the rotor blade18is in a stationary position.

Once the rotor blade18is lowered to the desired height, the rotor blade18is rotated as shown inFIG. 8Bto be generally perpendicular to the tower14. Rotating the rotor blade18is performed by attaching a first lifting line54to a first rotor portion204and a second lifting line198to a second rotor portion206. The first rotor portion204of the rotor blade18may be supported using the first lifting line54, the first winch52, the integrated lifting apparatus40, and the first temporary support104in combination. Similarly, the second rotor portion206of the rotor blade18may be supported using the second temporary support152in combination with the second pulley system196and the second lifting line198. In this exemplary embodiment, the rotor blade18may have a weight that exceeds the lifting capacity of the integrated lifting apparatus40if used alone, but does not exceed the lifting capacity of the integrated lifting apparatus40together with the first temporary support104and the second temporary support152when used in combination in the manner described above.

Once the rotor blade18is removed, a replacement rotor blade may be inserted in much the same manner as described above regarding the removal of the rotor blade18, but with the steps performed in reverse. While not shown, according to an alternative embodiment, the second temporary support152may be decoupled from the nacelle12prior to the first temporary support104being decoupled from the hub16using the integrated lifting apparatus40.

According to this exemplary embodiment, after removing the first temporary support104, the second temporary support152may be decoupled from the nacelle12by removing the fourth, fifth and six connecting structures170,172,174. The second temporary support152may then be removed using the integrated lifting apparatus40, as similarly discussed above with respect to the first temporary support104.

Replacing the rotor blade18in this exemplary manner, prevents the need for a jack-up vessel as described above, which saves both time and money. Additionally, using the first temporary support104and the second temporary support152greatly increases the lifting capacity of the integrated lifting apparatus40without significantly increasing the size and weight of the integrated lifting apparatus40.

While the present invention has been illustrated by the description of various embodiments thereof, and while the embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. The various features discussed herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.