CONFIGURED FOR LIFTING BY SAID METHOD

This invention relates to a blade lifting method and apparatus. In particular, the invention relates to lifting a wind turbine blade safely when constructing or disassembling a wind turbine, and to methods and apparatus for doing the same.

A wind turbine hub, to which the wind turbine blades are connected, rotates as the wind applies lift to the blades. The rotation of the hub is coupled to a gearbox and generator in order to convert the rotational motion into electrical energy. Due to the size of the blades and hub, it is often necessary in wind turbine construction, transport, and handling, to first position the hub at the nacelle, on top of the wind turbine tower and subsequently to lift the wind turbine blades up to the hub where they can be connected. Although some blades may be preinstalled and connected to the hub to form a rotor prior to positioning it at the nacelle, it is not always practical to lift the entire rotor assembly in one manoeuvre due to its prohibitively large size. It is also necessary when disassembling a wind turbine or when servicing blades, to lift the blades down from the hub after they have been disconnected.

Modern wind turbines are designed with increasingly high towers in order to access higher wind speeds, thereby maximising the energy they can extract from the wind. At higher altitude the wind is also less prone to turbulence due to the increased distance from the ground. However, as the height of the wind turbine tower increases it becomes harder to lift the wind turbine blades safely for connection or disconnection to or from the hub. In addition to the increased lifting height, wind turbines having higher towers also typically have longer blades with greater mass. This further impacts upon the safety of lifting the blade. Furthermore, larger blades are more susceptible to the effects of wind during a lifting manoeuvre, making it harder still to lift them safely.

In WO 2012/062352 A1 , a wind turbine blade is lifted by positioning a first lifting sling around a root end and a second sling around a tip end. Each of the slings is suspended from a lifting beam, connectable to a crane. A similar lifting arrangement for a wind turbine blade is disclosed in DE 20 2010 003 033 U1 . Here, a sling is used to support the tip region and a cable is wrapped around the root region. The cable and sling are connected to a boom-type yoke for lifting. Also EP2003333 discloses a lifting arrangement using a yoke suspended from a lifting crane and two slings suspended from the yoke, each spaced longitudinally along the blade. In known lifting arrangements, a sling or strap around a blade tip- or mid- region, i.e.

outboard of the blade centre of gravity. May tend to damage the comparatively slender trailing edge unless supported by an additional cradle. These arrangements are also known although they generally need to be shaped such that they adapt to the blade surface at the relevant lifting point. This brings with it a cost and a need for the relevant cradle always to be available when lifting a blade of a given design. Moreover, the need to arrange a lifting sling outboard of a blade centre of gravity, in particular in a tip- or mid- region thereof, is easier to perform when a blade is on the ground than when a blade is fixed at a hub, atop a tower prior to dismantling. Furthermore, releasing a sling after raising and installing a blade is sometimes precarious or unreliable and can lead to a tendency for parts to fall to the ground during a remote release of a sling or/and cradle.

It has been suggested, for example in US2014/0127025, to lift a blade by means of three fixing units inside the blade, distributed around and close to the blade's centre of gravity. The blade is suspended from three such fixings via respective slings, each attached to a fixing through a respective hole in the blade upper shell surface. The slings can be attached to the fixings by technicians inside the blade. Although this method does not require the use of a sling around the blade, it imposes the load of the blade's full weight locally around the blade's centre of gravity because, in effect, the blade has only a one, local lifting area comprising three holes arranged close together. Moreover, the blade shell is thinner in blade regions outboard of the root, so that there remain some structural advantages from using the root as a lifting location. In addition, when a blade is lifted or lowered using a single lifting location, that lifting location can have the undesirable effect of acting as a pivot about which the blade can rock, making the blade more difficult to control while it is suspended, because it is more prone to being blown or nudged away from its intended lifting orientation. Long tag lines need to be used to maintain the blade in its desired orientation, but these can be less effective or unusable at considerable heights. Moreover, still in the arrangement per US2014/0127025, the fixings remain inside the blade after its installation and during turbine operation. This adds weight to the blade and raises the question whether or not the fixings are structurally sound before re-use when dismantling a blade for servicing or replacement.

Therefore, there is a need to provide an improved blade lifting method and apparatus, to enable a wind turbine blade to be lifted or lowered safely during the construction or disassembly of a wind turbine and addressing shortcomings of known arrangements. SUMMARY OF THE INVENTION

In a blade lifting method and apparatus according to aspects of the invention, the apparatus comprises a lifting sling to be removably passed internally through a set of port- holes in an outboard portion of a wind turbine blade, around a main longitudinal structural support member in the blade and suspended from a lifting apparatus. A further lifting apparatus is attached to the blade at its root prior to a blade lift. The mid- region of a wind turbine blade and its root region may thereby be supported during lifting by an external lifting means such as a crane. The invention thereby provides a simple means for reliably lifting or lowering a blade without requiring to pass a lifting sling externally around a tip- or mid-region of a blade. Moreover, the lifting gear fixed inside the blade is minimised, even while the blade is lifted from within. The invention is defined in the appended independent claims to which reference is made. Further, optional advantageous features are defined in the dependent claims.

In a first aspect, the invention comprises a method of lifting a wind turbine blade, the blade extending spanwise between a root end and a tip end, the blade having a suction side shell portion and a pressure side shell portion both extending chordwise from a leading edge to a trailing edge and defining a thickness therebetween, the blade further comprising a longitudinally extending internal structural support member extending across the thickness extent of said blade between a suction side spar cap and a pressure side spar cap, the blade further comprising a set of lifting port-holes at an outboard lifting location outboard of and nearby the blade centre of gravity; the method including suspending the blade at an inboard lifting location at a root region and at the said outboard lifting location; wherein the step of suspending the blade at the outboard lifting location includes passing an elongate lifting sling, suspended from a lifting element such as a crane, through the set of port-holes internally through the blade, such that the sling passes through both the suction and pressure side shell portions and externally around the longitudinally extending internal structural support member and externally around at least one spar cap. The method further includes lifting the blade; and when lifting the blade is completed, disengaging the lifting sling from the blade and retracting the sling from within the blade. By this method, it is ensured that the blade is lifted by positive engagement of the sling around a structural portion of the blade. A positive lift can be preferable to using gripper type lifting means which rely on friction force for keeping hold of the blade during a lift. Preferably, the sling may be suspended from a lifting element by attachment of a first and a second end of the sling to the lifting element. In embodiments, the lifting sling at the outboard location on the blade may be released from its lifting position by means of releasing one end of the sling suspended from the lifting element such that it is drawn away from the lifting element under the action of gravity. In doing this, the remaining length of the sling may be retracted from the blade by moving the lifting element away from the blade, preferably in an upwards direction, such that the sling is drawn, out, through the port holes at the outboard lifting location. Optionally, the method may make use of a lifting yoke such as a beam-type yoke, to be suspended from e.g. a crane. Inboard and outboard lifting apparatus may be suspended from the yoke. Alternatively, it may be preferred to suspend inboard and outboard lifting apparatus from respective lifting elements e.g. from two separate cranes, jibs or booms. This method ensures that the lifting loads on the blade are spread over two lifting locations, spaced spanwise apart and straddling the blade centre of gravity.

In a further aspect, the set of lifting port-holes at the blade outboard lifting location may comprise two pairs of port-holes, each port-hole being arranged adjacent the internal structural support member, wherein each pair of port-holes is provided in a respective suction or pressure side of the blade shell and wherein a respective one of each pair of port-holes is provided at a leading and at a trailing edge side of the internal structural support member, the lifting sling passing through each one of the port-holes of the set. In this way, the lifting sling passes through respective port-holes on both sides of the blade shell and through port-holes a both the leading and trailing edge sides of a main spanwise structural reinforcement member inside the blade shell. This arrangement gives stability to the lift, ensuring both a high level of security between the lifting sling and the blade as well as ensuring a high level of support to the blade by virtue of the sling passing around the blade's main structural element. According to this aspect, the blade may in particular adopt a predominantly lying horizontal and flat orientation, which is to say that the blade's spanwise and chordwise axes may be predominantly horizontally arranged, or that the blade thickness direction may be mainly aligned with a vertical direction.

In an alternative embodiment, the set of lifting port-holes at the blade outboard lifting location may comprise a single pair of port-holes arranged on opposite sides of the blade shell, preferably both arranged on the shell at a leading edge side of the blade main elongate support structure. Preferably the port-holes may be arranged adjacent the leading edge side of the blade main elongate support structure. According to this aspect, the blade may in particular adopt a partial predominantly horizontal orientation, which is to say that the blade's spanwise axis may be predominantly horizontally arranged, or that the blade thickness direction may be mainly aligned with a horizontal direction. A blade chordwise direction may be mainly aligned with a vertical direction.

According to a further aspect, the method may include coupling together, inside the blade shell, a first and a second length of the lifting sling. To this end, there may be provided a respective bridging end at each sling length, forming an extremity of the sling length distal from its tack end. The bridging end of a sling length may in particular include bridging support points for attachment of a bridge link connecting a first and a second length of the lifting sling and enabling lifting therewith. Preferably, the first and second lengths of the lifting sling may be coupled together inside the blade and at a location adjacent the longitudinally extending internal structural support member. This may make it easier for a technician positioned inside the blade during installation or dismantling of the lifting sling to connect it together or to release the sling coupling connection. In some aspects, it may be envisaged to couple together respective bridging ends of the lengths of the lifting sling at a location outside the blade, for example lying against the shell, underneath or alongside the internal main longitudinal structural support member.

In a further aspect, the method may include passing a first length of the lifting sling once through three port-holes of a set of four lifting port-holes. Thereafter, second length of said lifting sling may be passed once through a fourth port-hole of the set of lifting port-holes. These steps thereby bring respective bridging ends of the first and second sling lengths into abutment. The term "abutment" in this context may designate a proximity between respective bridging ends sufficient to allow coupling together thereof by means of a bridge link, for example, by an appropriately positioned technician. According to this method step, a first sling length, in particular a bridging end thereof may be passed first through a first port-hole on one side of a blade shell to the interior of the blade and thereafter out through a second port-hole in the opposite side of the blade shell. The first sling length may thereby be brought into a intermediate position, passing through the blade from one side to the other and at a leading edge side of the main internal support member. An intermediate position of a first length of said lifting sling may encompass the first length being

suspended at its tack end from a lifting implement. In aspects, the first sling length may be fed from a starting position inside the blade, with a tack end and a bridging end inside the blade, to an intermediate position passing through the blade from one side to the other and with its tack and bridging ends outside the blade. From this starting position, the first length of the lifting sling may subsequently be suspended at its tack end from a lifting element. Alternatively, the first length may be fed from a starting position outside the blade, with a tack end and a bridging end outside the blade, to an intermediate position passing through the blade from one side to the other and with its tack and bridging ends outside the blade. In this latter case, the starting position may also encompass the first length being suspended at its tack end from a lifting implement.

The step of passing a first length of the lifting sling through a third port-hole may include passing a bridging end thereof from an intermediate position outside the blade at an initial leading or trailing edge side of the main internal longitudinal structural support member, to a location inside the blade at an opposite side of the said structural support member. This may be achieved for example by means of a reaching implement operated from inside said blade. A technician inside the blade preferably positioned at a side of the main support member opposite to the side at which the first length extends in its intermediate position may be equipped with a reaching implement such as a hooking rod. This may allow ready retrieval of the bridging end of the first length to the inside of the blade at the same side as the technician. The first length of the lifting sling may thereby extend substantially around and underneath the main blade support structural member.

In embodiments having only two port holes at an outboard lifting location, a lifting sling may be threaded into position from a starting position inside the blade or outside the blade. Threading may optionally, preferably be accomplished with the assistance of a technician, optionally positioned inside the blade. The blade may e.g. be held with its chordwise direction towards the vertical. For a continuous sling, i.e. a sling extending in an unbroken length between two tack ends thereof, and starting for example with the lifting sling outside the blade, one end thereof may be passed in through a first port-hole on one side of the blade shell and out through a second port-hole on an opposite side of the blade shell. The sling may thereby extend through the blade, from one side to the other on one side of the main structural support element. In this case, a starting position for threading the sling may encompass its other end being already suspended from a lifting implement. After threading, its complementary end may be suspended from a lifting implement.

Alternatively, starting with a lifting sling inside the blade, one end thereof may be passed out through a first port-hole on one side of the blade shell and another end thereof may be passed out through a second port-hole on an opposite side of the blade shell. The sling may thereby extend through the blade, from one side to the other on one side of the main structural support element. In this case, at least one end of the sling may subsequently be suspended from a lifting implement such that both tack ends are appropriately suspended for lifting. By way of example, a continuous sling may be suspended at one end from a lifting implement with its free end hanging in the vicinity of a port-hole on one side of the blade shell. A technician may reach the free end and draw it through the relevant port-hole to the inside of the blade, before feeding it through a second port-hole on the opposite side of the blade. A technician may use a reaching implement to gather the sling free end. Where a sling is provided in a first and a second length, the sling may be threaded in any appropriate way through a set of two port-holes and may be coupled together at respective bridging ends thereof. The bridging ends may, for example be coupled together at a coupling location inside the blade, preferably alongside the main elongate support member. Alternatively, the bridging ends may, for example be coupled together at a coupling location outside the blade, preferably alongside the shell in the vicinity of the blade's main elongate support member and preferably within reaching distance of a technician positioned inside the blade during threading of the sling. In one aspect, respective first and second lengths of a lifting sling may hang in an intermediate position with their respective bridging ends on either side of the blade shell and nearby a respective port-hole of a set of two port-holes. Each bridging end may be fed in through a respective one of an opposing pair of port-holes and coupled together inside the blade. Alternatively, one bridging end may be fed in through one port-hole and out through an opposing port-hole, to be connected to the other bridging end of the other sling length outside the blade. A suitable bridge link may be any connection component or element capable of coupling the respective bridging ends. A shackle or strap or nut-and bolt or a length of high-strength rope or other such connectors may be chosen depending on circumstances. Preferably, one or more bridge links may couple the respective bridging ends at their respective bridging support points. Thereby, loads may be transferred along the lifting sling, between respective first and second lengths thereof, via respective bridging support points and said bridge link or bridge links.

In a further aspect, when lifting the blade is completed, the step of disengaging the lifting sling from the blade may include uncoupling the bridge ends of the lifting sling lengths from within the blade. This operation may be carried out for example by a technician inside the blade operating on the bridging ends inside the blade, or by a technician inside the blade and reaching through a port-hole to carry out the uncoupling step on bridging ends coupled outside the blade. Optionally, the blade may further include a cap at one or more or at each of the port-holes of a set of lifting port-holes. When lifting the blade is completed, the step of disengaging the lifting sling from the blade may thereby include closing one or more or each port-hole, by applying a respective cap from within the blade. Also this step may optionally, preferably be carried out by a technician from inside the blade. The caps may be removably secured in position at a respective port-hole. Optionally, the caps may be provided in pairs of caps with a tensioning element extending between an inside face of each cap of a pair of caps. A suitable tensioning element may fully or partially include a spring or elastic connecting line. Optionally, the tension force applied by the tensioning element between two caps may be adjustable. The tensioning element will preferably be capable of imparting sufficient force between the closure caps to maintain these in a closed position when seated in respective port-holes. Optionally, the tensioning element may constitute the main or only retaining element for the caps in position in the port-holes during operation of a wind turbine blade. Preferably, each pair of caps may be configured to close a pair of port-holes of a set of lifting port-holes, the pair of port-holes being arranged respectively on opposite, suction and pressure, surfaces of a blade. Preferably, each pair of caps may be configured to be manipulated, preferably from within a blade, from a closed position at respective said port-holes to generate an open position of a pair of said portholes. This operation may be carried out for example by a technician inside a blade.

Alternatively, this may be carried out by a technician outside the blade e.g. on one side thereof by, for example, reaching in through one port-hole with one cap of a connected pair of caps, to thereby seat it in an opposite port-hole, after which the remaining cap may be seated in the complementary port-hole. A technician may additionally use a reaching implement when positioning or removing closure caps.

In a further aspect, the blade may additionally comprise recessed rims around an external surface of each port-hole of a set of lifting port-holes. Still further optionally, a resilient material ring may be positioned between each cap and each rim. Preferably, a cap may be seated in a recessed rim such that the cap outer surface sits flush with the blade aerodynamic surface. Preferably, a resilient material ring may create a dirt-proof and/or waterproof seal between the inside and the outside of the blade. Preferably, the action of a tensioning element retaining the cap in place may exert sufficient closing force on the cap to thereby maintain a seal between the cap, a resilient material ring and the blade shell.

Optionally, the blade may further comprise spar cap reinforcements between opposing spar caps and adjacent at least two port-holes of a set of lifting port-holes. This arrangement may provide additional structural support to a blade shell locally around a port-hole. In particular, this arrangement may provide additional structural support at the periphery of a port-hole which, during lifting using the sling, may present a stress-concentration point on the blade shell. In particular a blade main longitudinal internal structural support member may comprise a longitudinally extending shear web or a pair of shear webs arranged side- by-side. Each shear web may extend in a thickness direction of a blade, between spar caps in the blade shell suction and pressure sides. In a manner known per se, spar caps may constitute longitudinally extending structural elements in a respective blade shell, serving, in conjunction with a shear web, to carry bending loads longitudinally on the blade and thereby to give the blade stiffness and resilience. In order to prevent, during lifting, local overloading of a blade by a sling at a location adjacent a port-hole, a spar cap reinforcement may be interposed between respective opposing spar caps at a suction and at a pressure side of a blade shell immediately adjacent a relevant port-hole. A relevant reinforcement may extend from one spar cap, along an edge of a port-hole to the opposite spar cap along an edge of the opposite port-hole. Alternatively, a relevant reinforcement may extend from one spar cap, along an edge of a port-hole to a portion of a shear web, distal therefrom. Preferably, one or more respective port-holes may be arranged at a location on a blade shell immediately adjacent a spar cap, in particular, outboard of a spar cap in a chordwise direction of the blade. Optionally, the reinforcements may be provided at one or both respective leading or trailing edge sides of a spar cap at a pressure or at a suction side of said blade, or at both sides.

In further aspects of the method of the invention, the blade may comprise a support sleeve extending between corresponding port-holes on opposite respective pressure or suction sides of the blade shell. Preferably a support sleeve may extend between port-holes adjacent each of a respective leading edge and/or trailing edge side of the internal structural support member. Preferably, a support sleeve may comprise sleeve walls extending in a thickness direction of a blade between two collars, each surrounding a respective one of opposing port-holes. In this way, a support sleeve may define a passage from one port-hole on one blade surface to its counterpart port-hole on an opposite blade surface. Hence, when in position through a relevant blade, a lifting sling may pass through the blade inside a support sleeve.

Optionally, a support sleeve may be provided with a reach-through hole through a wall thereof. A reach through hole may provide access from outside the sleeve to interior parts of the sleeve. This may include providing access from outside a sleeve, through a part of the sleeve to port-holes at a blade surface. Where the length of a sleeve exceeds the normal reach of a technician, or of a technician with a reaching implement, then more than one reach-through hole may be provided in a sleeve. For example, at least one reach- through hole may be provided at each end of a sleeve, nearby a sleeve collar, preferably within reach of a sleeve collar or port-hole. One or two or more such reach-through holes may be provided. Preferably a reach-through hole may thereby bring an interior region of the blade, external of the sleeve, into communication with an interior region of the sleeve. Thereby, the port-holes in a blade shell may be in communication with the interior of the blade via the reach-through hole in the sleeve. The reach-through hole may in particular allow a technician, inside the blade, to reach to a port-hole, in particular to grasp a relevant end of a sling or sling length, with or without a tool therefor, or to seat or displace a relevant closure cap at a port-hole aperture.

Still further, the invention may extend to a wind turbine blade configured for lifting by the method described herein or defined in any appended claim. The blade may in particular comprise a set of lifting port-holes at an outboard lifting location nearby and outboard of the blade's centre of gravity. A set of lifting port-holes may be closed by one or more pairs of caps, each pair of caps being connected by a tensioning element and with one cap of a relevant pair closing a respective one of a suction side and an opposite pressure side porthole in the blade. Preferably, the method of lifting a blade at a said outboard location may be complemented by a lift at the blade root end by any suitable means or method such as by means of a root sling or strap around the root end. Such a root sling or strap may be suspended from a lifting element which may be independent from the outboard location lifting element or associated therewith, for example by means of a yoke such as a beam or boom type lifting yoke.

Optionally, the blade per the method of the invention may additionally be provided with a lifting hole at a root end, which may be a single lifting hole at said root end. Optionally, the root end lifting hole may be configured to allow lifting of the root end by suspending the blade at its root region in conjunction with suspending the blade at an outboard lifting location, as described above, the method additionally including: passing a first end of a lifting connector through the lifting hole to an interior root region within the blade shell; providing within the interior root region of said shell a lifting bar having a first end region and a second end region spaced from each other; connecting, within said shell, said first end of said lifting connector to said lifting bar, such that said lifting connector engages with said lifting bar at or near a middle portion thereof between its first and second end regions; bringing said lifting bar into supporting contact with the inside surface of the interior root region of said shell at respective first and second portions of the inside surface of the interior root region of said shell; and lifting the blade using the lifting bar and the lifting connector..

According to this latter aspect, a wind turbine blade may be lifted without the need to wrap a sling or strap around the root portion of the blade. The lifting connector and lifting bar can be safely installed and/or removed by an engineer working within the blade root, thereby improving safely during the lift. During use, the lifting connector extends externally of the blade and internally of it. Preferably, the said lifting location and the said hole may be located spanwise inboard of the blade's main internal structural spar or shear web structure. Thereby, the lifting bar can be positioned inside the blade shell at its root region without being obstructed by or interacting with the blade internal structural reinforcement such as the blade main spar or main web (or main webs, as the case may be). For the avoidance of doubt, according to the method of the invention, the mid- or tip-region of the blade at which the outboard lifting location is located, lies outboard of the centre of gravity of the blade. Similarly, a root region of the blade at which the inboard lifting location is located, lies inboard of the centre of gravity of the blade. Preferably, the lifting bar is brought into supporting contact with inside surface portions of the interior root region of the shell at respective first and second shell wall portions which are spaced from each other e.g. at diametrically opposite sides of the lifting hole. Preferably, the lifting according to the invention is carried out such that the root end of the blade is supported via only a single lifting hole in the root region. The method preferably additionally comprises disengaging, when lifting the blade is completed, e.g. after attachment of the blade to a wind turbine rotor hub, said lifting bar from the lifting connector, and retracting said lifting connector through the lifting hole. The lifting apparatus can therefore be safely and efficiently dismantled after the lift is completed. The method may additionally comprise removing the lifting bar from the blade shell once lifting the blade is completed. The lifting apparatus can therefore be safely and efficiently dismantled after the lift is completed. Moreover, the lifting apparatus thereby does not remain inside the blade during use. Preferably, the lifting of said root end is carried out using only a single lifting hole in the root region of the blade shell. The use of only a single lifting hole in the blade root avoids additional damage the structure of the blade. In this context, the hole may be located in a part of the root region which lies inboard of the main internal structural elements of the blade, such as its main spar or its main web/webs. The terms inboard and outboard are intended to designate relative proximity to or distance from the centre of rotation of the blade when positioned on a rotor hub. When applied to a lifting location along the blade, the terms outboard and inboard may refer to positions outboard or inboard relative to the blade centre of gravity.

In preferred aspects, the method may include positioning the lifting bar within the root region of the shell in a substantially horizontal orientation, and/or in an orientation which is substantially perpendicular to the lifting connector. The blade is therefore adequately and evenly supported by the lifting apparatus during the lift.

Preferably, each of the said first and second end regions of the lifting bar may be engageable with least one support pad for providing supporting contact with the inside surface of the interior root region of the blade shell. The support pads enable a large contact area to be established between the lifting bar and the blade shell, thereby improving the degree of support for the blade during the lift whilst avoiding damaging the shell. Preferably a support pad is arranged at each end of said lifting bar and carried thereon. Alternatively, one or more support pads may be arranged on the inside surface of said blade root region for engagement with said lifting bar prior to and during lifting. A support pad at one end of said lifting bar may comprise a single support pad or it may be a composite support pad, made up from multiple pads all at a same end of said lifting bar. The larger surface area of the support pads may reduce the local stress and strain in the blade shell in its root region.

Still preferably, the support pads may have a complementary shape to the inside surface of the interior root region of the blade shell. The support pads therefore readily engage with the blade shell or with the lifting bar, providing improved support during the lift. In aspects the support pads may exhibit a gripping high-friction surface to mitigate against slippage at the blade shell internal surface during use. Preferably the support pads are made from resilient material which recovers its shape after use. The material may preferably be or may comprise an elastomeric material. In aspects of the method, the connecting step may comprise locking the lifting connector to the lifting bar. This may be achieved by any suitable means, using fixing elements or locking elements and connecting elements of sufficient strength to carry the weight of the root end of the blade without rupturing. In particular, the method may include passing the first end of the lifting connector through an aperture in the lifting bar, and then locking the lifting connector to the lifting bar preventing accidental disengagement thereof. By way of example, the said locking may be effected by passing a locking pin through an aperture at said first end of said lifting connector. The lifting connector is preferably configured such that it is of narrow enough dimensions to pass through the lifting hole whilst still being securable to the lifting bar. Optionally, the lifting bar and lifting connector may exhibit one or more holes, apertures or eyes, allowing one of these to be threaded through the other, or allowing the two to be connected by a connecting piece such as a shackle.

In these and in further aspects, the step of suspending the blade at an outboard lifting location such as at its body region may include passing a first end of an elongate lifting sling externally around a longitudinally extending internal structural support member of the blade through one or two pairs of port-holes arranged adjacent the internal structural support member. In this context, each pair of port-holes may be provided in a respective suction or pressure side of the blade shell and with a respective one of each said pair of port-holes at a leading and at a trailing edge side of said internal structural support member. In this context a longitudinally extending internal structural support member of the blade may be a main spar, a main shear web or a pair of main shear webs. It is not excluded that there may be more than a pair of shear webs around which the lifting sling may pass, e.g. three or more, but these constructions are less likely. In this way, where a set of port-holes includes four such holes, a first end of a lifting sling may be passed through a port-hole at the uppermost blade shell surface, through the inside of the blade, past one side of its structural reinforcing elements and out through the lowermost shell surface, and then around the outside of the blade along the lowermost outer blade shell surface underneath the blade structural support, around and then up through a further port- hole in the lower most blade shell surface, at an opposite side of the structural

reinforcement member(s), upwards through the inside of the blade along the opposite side of the structural reinforcement member(s) before passing it out through another port-hole at the uppermost blade shell surface, from where it may be passed to a lifting link. This threading process may in particular be carried out while a second end of said lifting sling is connected or connectable to a suspended lifting link. By way of example, this procedure may be carried out by personnel positioned inside the blade and on either side of the main structural support member(s), one or more of whom may be equipped with a grabbing stick for pulling an end of the lifting sling in through a hole or for pushing an end of the lifting sling out to the outside and possibly up to a lifting link. In this way, a positive connection can be achieved between the lifting sling and the blade, even more so than by using a purely external sling. This may further reduce the risk of slippage of the blade from a purely externally positioned lifting sling. It should be noted, of course, that this procedure and other procedures requiring personnel to be inside the blade at a region outboard of the centre of gravity may only be performed in larger blades where there is preferably a minimum of fifty centimetres of internal clearance space between the uppermost and lowermost blade shell surfaces.

In a still further aspect, the lifting sling may comprise a first length and a second length and the method may include joining together, inside the blade shell, the first and second lengths of the sling at a bridging end thereof at a location adjacent the longitudinally extending internal structural support member. The bridging end of the first and second sling lengths may be connected by a longitudinal pin or by shackles or by a combination of these. Other fixing elements may also be contemplated provided these have the requisite strength to carry the blade weight at its mid- region without rupturing. According to this aspect, it may be advantageous for the first and second sling lengths to be of different effective lengths between their respective lifting link connection end, which may be called a tack end, and their bridging end. In this way, for example, a bridging end of a first length of said sling may be lowered from a lifting link to which its tack end is attached, though a port-hole in the shell uppermost surface and threaded through the blade around the internal support members and back up into the inside of the blade, while a second, shorter length of the lifting sling, also suspended by its tack end from a lifting link, may be passed only through the other of a pair of port-holes in the uppermost shell surface. In this way, the respective different effective lengths of the first and second sling lengths allows their respective bridging ends to meet adjacent one side of the blade's main internal structural members.

BRIEF DESCRIPTION OF THE DRAWINGS

Some features of the invention and various aspects and implementations thereof will now be described, by way of example only, and with reference to the accompanying schematic drawings, in which: Figure 1 shows a simplified, three-dimensional view of a wind turbine blade;

Figure 2 shows a schematic orthogonal view of a lifting method and apparatus according to aspects of the invention;

Figures 3a-c show schematic, not-to scale, simplified cross-sectional views of a mid- or tip- portion a wind turbine blade to be lifted according to aspects of the invention;

Figure 4 shows schematic views of a lifting sling according to aspects of the invention;

Figure 5 shows a schematic three-dimensional view of a support sleeve according to aspects of the invention;

Figure 6 shows a schematic three-dimensional view of a detail of a port-hole according to aspects of the invention ;

Figure 7 shows a schematic orthogonal view of a pair of closure caps according to aspects of the invention; Figure 8 shows a schematic cross-section view of detail of a closure cap nearby a port-hole aperture according to aspects of the invention;

Figures 9a-9b show a schematic cross-section views of details of closure cap pairs at a pair of port-holes in a wind turbine blade;

Figure 10 illustrates schematically an end view of a blade showing an alternative root-end lifting method according to aspects of the invention;

Figure. 1 1 shows schematically and from a perspective view, further features of the alternative lifting method per Fig. 10;

Figure 12 shows schematically, an alternative lifting method according to aspects of the invention. DETAILED DESCRIPTION

Figure 1 shows a simplified, schematic, not-to scale, three-dimensional view of a wind turbine blade 10. The blade 10 exterior is defined by a shell which extends spanwise between a root portion 1 1 and a tip 12 and chordwise between a leading edge 15 and a trailing edge 16. Arrow 202 indicates an approximate chordwise direction, while arrow 204 indicates a spanwise direction, corresponding to the length direction of the blade. The chordwise direction 202 lies substantially perpendicular to the spanwise direction 204 and is defined by a straight line extending between the leading and trailing edges 201 , 16. A thickness direction of the blade 206 typically extends perpendicular to both the chordwise 202 and spanwise 204 directions, at any given spanwise location along the blade 10. It will be appreciated that the chordwise direction 202 varies along the blade length, mainly to accommodate for greater blade operating speeds near the tip 12 than near the root 1 1 . Consequently, also the thickness direction 206 can vary along with the progressively shifting chordwise direction 202. The approximate location of the blade's centre of gravity is indicated by arrow 125. A windward or suction side of the shell is separated in a thickness direction 206 from a leeward or pressure side of the blade shell. A maximum chord axis (not shown) runs from the leading edge 15 to the trailing edge 16 at the spanwise location exhibiting the greatest chord length.

The blade 10 terminates at a most inboard end of its root 1 1 in a pitch bearing ring face 22 for connection with a corresponding bearing ring on a rotor hub (not shown). The connection may be made by means of stud bolts securely fixed into holes formed in the blade shell wall at its root 1 1 , where the blade shell may be thickest, and secured through holes in a corresponding bearing ring (not shown) at the rotor hub.

The blade shell defines the aerodynamic shape of the blade 10 and is typically internally structurally reinforced and supported by a longitudinally extending main reinforcing structure such as a spar or shear web (not shown in Fig. 1 ) which extends in a thickness direction 206 between a blade suction or a blade pressure surface and in a spanwise direction 204 from a blade root region 1 10 through a mid- or body region 130, to a tip region 120 or tip 12. In some cases a main shear web may comprise a pair of mainly coextensive shear webs arranged side-by side. It is not excluded that the main shear web may comprise more than two shear webs. In general, the main reinforcing structure extends longitudinally along the internal length of the blade 10, bridging the greatest internal thickness dimension along the blade. In Fig. 1 , respective blade shell surfaces are indicated as an upper shell surface 210 and a blade lower shell surface 212, either of which may be at a leeward or windward face of the blade, depending which way up it is oriented. The internal reinforcing structure supports the shell and transmits operating or

environmental loads on the entire length of the blade 10 during operation to its root 1 1 . The internal reinforcing structure also ensures and maintains a spacing or separation in a thickness direction between the opposing pressure and suction surfaces of the shell which thereby improves the blade stiffness.

Moving outboard from the pitch bearing face 22, the blade root 1 1 is followed by a blade root region 1 10 and then a blade root transition region 135 towards the blade shoulder 230. Thereafter, the blade mid-region 130 is followed by the blade tip-region 120 which runs to the tip 12.

The cross-section of the blade 10 changes and evolves from the round root portion 1 1 towards the slender aerofoil-shaped tip 12. First, in the root transition region, the blade widens in a chordwise direction and tapers down gradually in a thickness direction to the shoulder 230. The blade becomes progressively flatter, i.e. shallower in the thickness direction and shorter in a chordwise direction towards the mid-region 130. From the mid- region 130 through the tip-region 120 to the very tip 12 of the blade span, the blade becomes progressively more flat, exhibiting a recognisable aerofoil-shaped cross-section. The length of the chord also decreases towards the tip 12. In larger blades, perhaps having a length 50m or 60m and above, the internal thickness dimension inside a blade in its mid-region 130 can be greater than 50cm, sometimes 1 .5m or 2m or more. An internal root dimension may easily exceed 2m, perhaps even reaching 4m or more.

The blade 10 is typically made from lightweight laminated composite materials such as fibre-glass in a resin matrix. Additional reinforcing materials may be used in certain regions while lightweight spacer materials such as foam and balsa wood may be used in places to improve stiffness without adding weight. In the view depicted in Figure 1 , the blade is shown at an orientation corresponding approximately to a horizontal longitudinal axis and horizontal maximum chord axis. This may correspond approximately to a desired lifting orientation for horizontal type lifting operations or for horizontal type blade-to-hub attachment operations. In use, the blades 10 are connected to a hub to form a rotor usually comprising three blades. When the blades 10 are pitched into the wind, air passes over the leading edge 15 towards the trailing edge 16 and beyond, creating lift as a result of the blade's aerofoil shape. The rotor is connected via its hub to a rotating shaft which drives a generator (not shown) in a nacelle (not shown). In general, and according to aspects of the invention, a blade 10 may be lifted at two lifting locations respectively spanwise inboard and outboard of the blade's centre of gravity 125. In particular, a blade 10 may be lifted at a first lifting location 135 inboard of the blade centre of gravity 125 and at a second lifting location 145 outboard of the centre of gravity 125. As already mentioned, blade 10 comprises a root portion 1 1 and a blade tip 12. As mentioned, root portion 1 1 is typically circular or round when viewed in a chordwise cross- section and terminates in a circular pitch-bearing face 22. The whole root region and the root 1 1 provide structural strength where loading on the blade 10 will be highest, namely at its connection to a hub. The approximate location of the blade's centre of gravity 125 is indicated.

According to aspects of the invention, a blade 10 may be lifted or lowered by means of a lifting element such as one or more cranes, possibly by means of a longitudinally extending yoke from which it may be suspended. In particular, according to aspects of the invention, it may be lifted at a first location 135 at its root 1 1 and inboard of the blade centre of gravity 125, and at a second location at or nearby a mid- 130 or tip-region 120. The second lifting location 145 may in particular lie outboard of the blade centre of gravity 125. For this purpose, a yoke may be a boom type yoke having a longitudinal extent extending between an inboard end and an outboard end. The yoke (not shown) may be suspended from a crane cable (not shown).

According to aspects of the invention, and as illustrated in Figs. 2 and 12, a blade 10 may be lifted at two lifting locations, namely at an outboard lifting location 145 and at an inboard lifting location 105. An outboard lifting apparatus 300 including a lifting sling 320 may be suspended from a lifting element such as a crane (not shown) via a lifting link such as a hook for lifting a blade 10 at an outboard lifting location 145 thereof. At its root end 1 10, the blade 10 may be supported by an inboard lifting apparatus 600 which may include e.g. a strap 620 suspended from a same or additional lifting element via a lifting link such as a hook. Each lifting link at a respective outboard and inboard lifting location may optionally be suspended from a yoke (not shown) which may comprise a boom or beam type yoke. Such a yoke may be suspended from a lifting element such as a crane. Alternatively, a separate e.g. crane may be used for suspending a blade 10 at respective outboard and inboard lifting locations 145, 105. As shown in Fig. 2, in embodiments according to the invention, the blade 20 may adopt a generally flat horizontal orientation, with both spanwise 204 and chordwise 202 directions lying more or less horizontal and the thickness extent 206 being roughly vertical. By contrast, as shown in Fig. 12, in embodiments according to the invention, the blade may adopt a partially horizontal orientation, with its spanwise extent 204 and thickness extent 206 being generally aligned with a horizontal plane, while a chordwise extent 202 is more or less vertical. In each case, a lifting sling 620 is passed through a set of lifting port-holes 80 in the blade 10. In the arrangement shown in Fig. 2, a four-hole set of lifting port-holes 80 may be preferred for the lifting sling 320 at the outboard lifting location 145. In the arrangement of Fig. 12, a two-hole set of lifting port-holes 80 is implemented at the outboard lifting location 145.

Figs. 3a-c illustrate an outboard lifting apparatus 300 which may comprise a lifting sling 320 in co-operation with a set of four lifting holes 80. The sling 320 may be passed partly through the inside of a blade 10 at an outboard lifting location 145 relative to the centre of gravity 125, namely at a mid- or tip-region of the blade 10. The main internal reinforcing structure in a blade 10 may be in the form of a spar (Fig. 3a) or a single shear web (Fig. 3b) or a double shear web (Fig. 3c) or other suitable structure. Other configurations of a main reinforcing structure 414 may be envisaged. Preferably, the lifting sling 320 passes through the inside of the blade 10 but always outside the main reinforcing structure 414. In Figs. 3a- c, an internal blade main longitudinal reinforcing structure 414 is shown, extending in a thickness direction 206 of the blade, between spar caps 424, 434 at a respective suction side and pressure side of the blade 10. In the case of one or more shear webs, these typically end somewhat short of the blade root portion 1 1 , while in the case of a main spar, this typically blends into the root portion walls at the blade root 1 1 .

The lifting sling 320 may be suspended from a lifting yoke, for example at its outboard end for lifting the body portion 130 of the blade 10. As shown in Figs. 3a-c, with the blade spanwise axis 204 lying approximately horizontal, and with a chordwise direction 202 also generally approximately horizontal, the blade 10, beyond its root end 1 1 , may present a generally uppermost 210 and a lowermost 212 aerofoil surface. A free end of a sling 320 may be passed from the outside of a blade 10 through a first hole 901 , 904 in an uppermost blade surface and thereafter through the inside of the blade 10 before being passed out through a further hole 902, 903 in the lowermost blade surface, following which it may be passed back into the blade though a further hole 902, 903 in the lowermost surface, through the inside of the blade 10 and back out through a second hole 901 , 904 in the uppermost blade surface. Thereafter, the sling 320 may be suspended from a lifting arrangement such as a yoke or crane hook. Optionally the holes of a set 80 of holes may be provided in complementary pairs of holes 901 , 902; 904, 903 each at an opposing pressure or suction side of the blade. Preferably, each one of a pair of uppermost surface holes 901 , 904 is provided at an opposite side of a blade main reinforcing member 414, with a first hole 901 at a leading edge 15 side of the main supporting member 414 and a second hole 904 at its trailing edge 16 side. Preferably, each one of a pair of lowermost surface holes 902, 903 is provided at an opposite side of a blade main reinforcing member 414, with a first hole 902 at a leading edge 15 side of the main supporting member 414 and a second hole 903 at its trailing edge side 16. These holes may equally be described as a pair of leading edge holes 901 , 902, each on a respective upper and lower blade surface, and pair of trailing edge holes 904, 903, each on a respective upper and lower blade surface. The holes 901 -904 may be in the form of spanwise extending slots. The lifting sling 320 may be shaped as a wide strap, having a considerable width dimension in relation to its thickness to thereby more evenly distribute the lifting loads at the outboard lifting location.

In a variant illustrated in Fig. 3c and in Fig. 4, the lifting sling may comprise a first length 130a and a second length 320b. Each length 320a, 320b may have a suspension end 340 (or tack end), for connection to a lifting device and a bridging end 360 for connection to each other via a bridge link 375. In use, the bridging ends 360 may be connected together inside the blade 10, at a leading edge side or at a trailing edge side relative to a main reinforcement member 414, for example by means of a bridge link 375. Preferably, a first length 320a has a longer effective length dimension than a second length 320b. This ensures that their respective bridging ends 360 meet at one side of the main reinforcement ember 414 when the sling lengths 320a, 320b are respectively threaded into a lifting position inside and outside the blade 10. Preferably, the first sling length 320a passes through the blade down through an uppermost surface and a lowermost surface at one side of a main reinforcement member 414 and back again up through the lowermost blade surface at an opposite side of the main reinforcement member 414 and inside the blade 10. Conversely, a second length 320b may simply pass down through an uppermost blade surface such that its bridging end 360 is located inside the blade at the same side of the main reinforcement member 414 as the bridging end 360 of the first length 320a. This is illustrated by way of example at Fig. 3c. This embodiment avoids the need to feed a free end of the sling 320 back up to a lifting arrangement after threading through the blade 10. It also allows disengagement of a lifting sling 320 without removing a tack end thereof 340 from a lifting arrangement.

Also shown in Fig. 3c and 3b are reinforcement members 500 inserted in a lip between a shear web and the edge of an adjacent port-hole. The reinforcement member may have a C-shape, which a main section connecting end flanges. Each end flange may lie along a portion of a spar-cap 424, 434 thereby functioning as a load distribution member at the support point between a sling 320 and a blade 10. Preferably, a reinforcement member 500 may be provided between each pair of opposing port-holes in any set 80 of port-holes.

Still further, in aspects of the invention, there may be provided a support sleeve 800 between corresponding opposite facing port-holes among a set of port-holes 80. An example is shown in Fig. 5. A support sleeve may comprise a wall 840 extending in a thickness direction 204 of a blade between two collars 810, each arranged around the inside surface at a respective opposing port-hole. A support sleeve 800 may serve to create a passage between communicating pairs of port-holes. Additionally, a support sleeve 800 may complement or adopt the function of a reinforcement member 500. To that end, a support sleeve 800 may be positioned with one wall abutting, connected to and coextensive with the thickness 206 extent of a support member 414, extending from one edge of one port-hole along a shell portion nearby a support member 414 to the

corresponding edge of an opposite port-hole nearby or at a support member 414. In this way, a support sleeve may present a channel or conduit through a blade, between opposing corresponding port-holes. Such a channel may serve as a passage through which a lifting sling 320 may extend. To assist in the implementation of the method of the invention, one or more through holes 850 may be provided in the wall of a support sleeve. A through hole 850 of this kind may allow a technician, possibly with the aid of a reaching implement, to better grasp free ends 340, 360 of a lifting sling 320 or lengths 320a, 320b thereof or to put in place or remove covering caps over the port-holes. To this end, it may be expedient to provide two or more reach-through holes 850, especially in cases where the length of the sleeve 850 would exceed or impede the reaching capacity of a technician inside the blade 10. In one embodiment, a through hole 850 may be provided in the form of a longitudinal gap extending along a significant part of the length of the sleeve 800. In one embodiment, a through hole may extend from one collar 810 to the other. In aspects, the invention may comprise positioning a covering cap 900 over a port-hole 80. With reference to Figs. 6, 7, 8 and 9a and 9b, a covering cap 900 may be sized to conform to a port-hole 80. Preferably, covering caps 900 may be provided in pairs. Preferably, any pair of covering caps 900 may be configured to securely cover two opposing port-holes 80 of a pair of port-holes on opposite faces of a blade 10. This may prevent humidity or dirt from entering a blade 10 during use. To this end, there may be provided a ring-shaped seal 825 around the periphery of a port-hole 80. Still preferably, a port-hole may be recessed in the blade shell surface to present a lip 805 supporting the peripheral edge of a covering cap 900 when positioned therein. Preferably, a seal 825 may be positioned around the periphery of a port-hole at its lip 805. In embodiments, the peripheral inward facing edge of a port-hole may be chamfered, to correspond with a chamfered edge of a covering cap 900 thereby ensuring a self-locating fit between the two. Preferably, a pair of covering caps 900 may be connected together by an elastic element 950 serving to keep the caps in position during use.

As illustrated in Fig. 9a, a cap 900 may be placed in position a blade by passing a first one of a pair of blades into a port-hole and then drawing a connected cap 900 through the interior of a blade 10 until its connecting element 950 is under tension. The second cap 900 of a pair of caps can then be pulled outward through an opposite port-hole and released such that it settles into the hole, 80 covering and sealing it. The tension arrangement between a pair of caps 900 can be seen in Fig. 9b which shows how two caps 900 of a pair pull against each other thereby biasing each other sealingly into position at opposite port-holes. When carried out by a technician from inside a blade, the technician may reach through a hole 84o in a wall of a support sleeve 800 to either position or remove a cap 900 from a corresponding port-hole. A reach through hole 840 may also allow inspection, visual or otherwise, of the seating of a covering cap 900 in its port-hole.

In other aspects, the invention may additionally comprise an inboard lifting apparatus for lifting a wind turbine blade, which blade has a shell extending longitudinally from a root region to a tip region and a lifting hole positioned at a lifting location in the root region of the blade, the lifting apparatus comprising: a lifting connector for passing through the lifting hole to an interior root region of the blade shell; a lifting bar having a first end region and a second end region spaced apart from each other, for providing supporting contact with respective first and second portions of the inside surface of the interior root region of said shell; and an engagement portion provided between the first and second end regions of the lifting bar, for engaging with a first end of the lifting connector. The lifting apparatus according to this aspect may, in particular, be connectable to a lifting element such as a crane or a lifting yoke. The first end of the lifting connector may be provided with an engagement member for engaging with the engagement portion of the lifting bar. The lifting connector can therefore be secured to the lifting bar prior to lifting, and the apparatus can be easily dismantled after lifting. In embodiments, the lifting connector may comprise a cable, cord, chain, rod, pole or bar or combinations of these. The lifting connector can preferably be passed easily through a lifting hole in the blade shell to engage with the lifting bar. Preferably, the first and second end regions of the lifting bar may have support pads for providing supporting contact with the inside surface of the interior root region of the blade shell. The support pads enable a large contact area to be established between the lifting bar and the blade shell, thereby improving the degree of support for the blade during the lift. At least part of the support pads for providing supporting contact with the inside surface of the interior root region of the blade shell may be made of a resilient, flexible material. The material therefore does not damage the interior of the blade shell when providing supporting contact. The support pads may have a complementary shape to the inside surface of the interior of a blade root region. The support pads therefore readily engage with the blade shell, providing improved support during the lift. Elements of this aspect are illustrated in Fig. 10 and Fig. 1 1 . Fig. 10 shows an end-view of a blade 10 seen in a spanwise direction from its root 1 1 . A blade shell internal surface 404 extends on the inside of the shell. The bearing ring face 22 comprises holes into which stud-bolts for attachment to a hub pitch-bearing may be fixed. The blade root portion 1 1 is free of the main reinforcing structure 414, hence, this is left out of the illustration, for clarity.

In accordance with aspects of the present invention, the blade root 1 1 may be provided with a lifting hole 906. By way of example, it may be desirable to locate the lifting hole 90, at an approximate distance within 2m or within 1 .5m or within 1 m from the most inboard end of the root portion 1 1 . This enables the lifting hole to be formed in the blade laminate whilst being clear of the stud-bolt receiving holes and the blade internal structural reinforcement 414.

With reference to Figs. 10 and 1 1 , an inboard lifting apparatus 600 may comprise a blade root lifting apparatus 650. This may comprise a lifting connector 658 and a lifting bar 652. The lifting connector 658 has a longitudinal extension between a first end 61 and a second end 62. The lifting connector 658 is illustrated in part in Fig. 10 and in part in Fig. 1 1 . A first end 61 of the lifting connector 658 is configured to pass through a lifting hole 90 formed through the wall of a blade 10, in particular at its root 1 1 . The second end 62 of the lifting connector 658 is configured to be positioned outside a blade 10, and is configured to be connectable to a lifting element (not shown) such as a crane or lifting yoke capable of to apply a lifting force to the lifting connector 658. The first end 61 of the lifting connector 658 is connectable to a lifting bar 652, as shown in Fig. 10. To that end, the lifting connector 658 may be provided with a lifting surface such as an aperture or hole, or other lifting surface which may include a flange, bracket, shoulder, recess, keyway or other

engagement surface. The lifting bar 652 has a longitudinal extent including two ends. The ends of the lifting bar provide a lifting connection between a blade 10 and the lifting apparatus 650. In particular, the weight of a blade, at its root 1 1 may rest on the ends of the lifting bar 652, preferably additionally via respective pressure pads 656 fixed either to the inside of the blade 10 e.g. at an inside surface 404 thereof, or fixed to the lifting bar 652. In some embodiments, the end regions of the lifting bar 652 may be adapted to be seated within pressure pads 656 provided fixed to the interior surface 404 of the blade root 1 1 . Alternatively, each end of the lifting bar 652 may be provided with a respective support pad 656 fixed thereto or removably fixed thereto. The two ends of the lifting bar 652 are spaced apart at opposite ends of a middle portion to which a lifting connection can be made together with the lifting connector 658. A fixing element 654 may be provided for securing the lifting connector 658 and the lifting bar in mutual engagement. The fixing element 654 may be fixed at a position along the lifting bar 652 or it may be movable in relation to the lifting bar. A fixing element 654 may suitably be in the form of a shackle. Other devices may be used for this purpose according to preferences or to circumstances, such as a locking pin, snap-shackle, socket, strap or cable or other suitable fixing means such as a shoulder, recess or keyway. In embodiments, there may be more than one fixing element 654 spaced along the lifting bar 652. These may be fixed at the lifting bar 652 or movably arranged therealong, preferably at selectable, lockable positions. Optionally, a selectively movable or fixed retainer may be included to maintain a fixing element 654 in a predetermined position along the length of the middle portion of the lifting bar 652.

Optionally the position of the retainer may be moved and set at selectable positions along the length extent of the middle portion of the lifting bar 652. Thereby, optionally, the lifting connection between the lifting connector 658 and the lifting bar 652 may be selectably moved to any desired position along the length of the lifting bar 652. Hence, if desired, in relation to Fig. 10 or Fig. 1 1 , the lifting connection between the lifting bar 652 and the lifting connector 658 may be further towards one or other extremity of the lifting bar 652. On the other hand, in embodiments, it is not excluded that the fixing element 654 may be located at the mid-point of the lifting bar 652. A mark may be made on the lifting bar 652 to indicate to an engineer where the fixing element 654 should be located, and/or where lifting connector 658 should be connected to the lifting bar 652 by any other means. Each support pad 656 may comprise a plate, for example a rigid or steel plate, connectable to an end of the lifting bar 652. In some embodiments, the support pads 656 may comprise a resilient, flexible material. In use, each of the pads 656 engages with the inside 404 of a blade 10 at its root portion 1 1 . Figure 10 illustrates in particular the disassembly of the blade root lifting apparatus 650 after the blade 10 has been lifted into position. Once the blade 10 has been lifted into position or lowered, the blade root lifting apparatus 650 is removed by detaching the lifting connector 658 from the lifting bar 652, by releasing the fixing element 654. The lifting connector 658 is then lifted out of the lifting hole 90, in the direction of the top arrow. Either before or after the removal of the lifting connector 658 from the blade 10, the lifting bar 652 may be removed from the blade 10 altogether. This may be undertaken by an engineer in the root portion 1 10 releasing the connector 658 and moving the lifting bar downwards in the direction of lower arrow. In some embodiments, the lifting bar 652 may be disengaged from the support pads 656 prior to removing the lifting bar 652 from the blade walls 404. The support pads may remain within the blade 10 or these may optionally be removed separately from the lifting bar or together with it.

The lifting hole 90 that remains in blade 10 can be sealed when the lift is completed. In some embodiments, the hole 90 is filled in with blade laminate, a plastic plug, sigmaflex, or flexible sealer. This can be drilled out easily if the lifting hole 90 is needed again for future lifting.

The blade root lifting apparatus 650 or 300 can be fitted into the blade 10 while secured on the ground or while it is attached to a hub. Lifting bar 652 may be positioned in the blade root by an installation engineer, and lifting connector 658 may be inserted into lifting hole 90 and connected to the lifting bar 652. The lifting connector 658 could be a tubular bar, for example a scaffolding bar. In alternative embodiments the lifting connector 658 could be one or more cables, for example flexible steel cables, or one or more cords, chains, rods, poles, and/or bars. Lifting bar 652 could be any bar, for example, a tubular bar, for example a scaffolding bar. In alternative embodiments the lifting bar 652 comprises an I- beam, with a hook provided for connecting to the lifting connector 658. In further alternative embodiments, the lifting bar 652 may comprise an eye or aperture through which an end of the lifting connector 658 can pass. A fixing element 654 in the form of a locking pin may be passed through an engagement surface in a first end 61 of the lifting connector 658. Such an engagement surface may in this embodiment comprise a hole. A suitable locking hole may be substantially perpendicular to the length axis of the lifting connector 658. In the figures the lifting bar 652 is shown as substantially perpendicular to the lifting connector 658. In other embodiments this need not be the case and the support pads 656 need not be level with one another.

In some embodiments, fixing element 654 may comprise a releasable bracket or set of bolts to secure the lifting connector 658 to the lifting bar 652. Alternatively, the connector 654 may be a flexible cable, for example a steel cable, wrapped around or engaged with the lifting bar 652 and lifting connector 658. The fixing element 654 may be integral to either the lifting bar 652 or lifting connector 658. In embodiments in which the lifting connector 658 comprises a cable, the connector 654 may be part of the same cable.

The lifting method illustrated in Fig. 12 corresponds to the lifting methods in the

embodiments discussed above, save that a set 80 of lifting port-holes at an outboard lifting location 145 may comprise two port-holes. The chordwise direction 202 of the blade 10 may preferably be oriented towards the vertical during implementation of the method according to this embodiment.

It is envisaged that features from any of the embodiments described herein may be combined together, at least to the extent that it is not prohibited by the laws of physics or otherwise manifestly impossible, and similarly that the steps of the methods described herein may be likewise be combined together or performed in a different order to that described. For the avoidance of doubt, the term "lifting" may include the act or operation of lowering, especially a blade 10. The mid-region of a blade may alternatively be referred to as a body region. A blade leeward side may be known as a pressure side. A blade windward side may be known as a suction side. A blade shell typically comprises a suction and a pressure side or a suction and a pressure surface. References to a shell may be references to the physical wall of a blade. References to a spar or main spar or shear web or main shear web or main shear web or main shear webs, may be understood as references to a main elongate internal structural support member, or words to the same effect, or vice-versa. A reference to a lifting implement may be a reference to a crane or other suitable lifting apparatus. A reference to a crane may encompass technical equivalents thereof. Where a part is referred to in the singular "a", it may not necessarily be excluded that multiple such parts may be envisaged unless expressly excluded using the word "single" or "only one" or the like. Various modifications to the example

embodiments described above are possible without departing from the scope of the following claims.