EP4065835A1

EP4065835A1 - Modular wind turbine blade

Info

Publication number: EP4065835A1
Application number: EP20819623.8A
Authority: EP
Inventors: Anton Bech
Original assignee: Vestas Wind Systems AS
Current assignee: Vestas Wind Systems AS
Priority date: 2019-11-29
Filing date: 2020-11-27
Publication date: 2022-10-05
Also published as: WO2021104600A1

Abstract

In a first aspect of the invention there is provided a modular wind turbine blade. The modular wind turbine blade comprises first and second blade modules configured for connection end to end and a plurality of mutually spaced first inserts which each have a fixed end integrated with a connection end of the first blade module, and a free end which projects from the connection end of the first blade module. The free ends have a profiled contour. The modular wind turbine blade further comprises a plurality of mutually spaced second inserts which each have a fixed end integrated with the connection end of the second blade module and a free end which projects from the connection end of the second blade module. The free ends have a profiled contour. The free ends of the first inserts abut the free ends of the second inserts when the first and second blade modules are arranged end to end, and one or more connection cavities are defined between the profiled contours of adjacent pairs of abutting inserts. The modular wind turbine blade further comprises at least one connecting element configured for insertion into a respective connection cavity to connect the first and second blade modules together. The at least one connecting element has a first end and a second end. The first end has a profile configured to intermesh with the profiled contours of adjacent first inserts, and the second end has a profile configured to intermesh with the profiled contours of adjacent second inserts.

Description

Modular Wind Turbine Blade

Technical field

The present invention relates generally to wind turbine blades, and more specifically to a modular wind turbine blade having an improved joint between blade modules.

Background

There is a continuing desire to generate increased levels of power from wind power production facilities such as onshore and offshore wind farms. One way to achieve this is to manufacture modern wind turbines with longer blades. The provision of longer blades increases the swept area of the rotor, allowing the wind turbine to capture more energy from the wind.

However, transportation of large components, in particular long rotor blades, can be problematic as a wind farm site may be remote and difficult to access. To resolve this problem, a rotor blade may be designed as a modular assembly. Such a modular blade may be divided into two or more modules that are easier to transport and which are then assembled on-site. Ease of on-site assembly is therefore a significant factor for consideration when designing a modular blade.

A particular challenge in the design of modular wind turbine blades is ensuring that the joint between blade modules is sufficiently robust. Various types of joint have already been proposed, including bonded joints and bolted connections. It is against this background that the present invention has been developed.

Summary of the invention

In a first aspect of the invention there is provided a modular wind turbine blade. The modular wind turbine blade comprises first and second blade modules configured for connection end to end. The modular wind turbine blade comprises a plurality of mutually spaced first inserts which each have a fixed end integrated with a connection end of the first blade module, and a free end which projects from the connection end of the first blade module. The free ends have a profiled contour. The modular wind turbine blade further comprises a plurality of mutually spaced second inserts which each have a fixed end integrated with the connection end of the second blade module and a free end which projects from the connection end of the second blade module. The free ends have a profiled contour. The free ends of the first inserts abut the free ends of the second inserts when the first and second blade modules are arranged end to end. One or more connection cavities are defined between the profiled contours of adjacent pairs of abutting inserts. The modular wind turbine blade further comprises at least one connecting element configured for insertion into a respective connection cavity to connect the first and second blade modules together. The at least one connecting element has a first end and a second end. The first end has a profile configured to intermesh with the profiled contours of adjacent first inserts, and the second end has a profile configured to intermesh with the profiled contours of adjacent second inserts.

A plurality of connection cavities may be defined respectively between the profiled contours of adjacent pairs of abutting inserts. A respective connecting element may be received in each connection cavity.

The free ends of the inserts may define contact surfaces for engaging with corresponding contact surfaces of a respective connecting element. The respective contact surfaces may be angled such that inserting a connecting element into a connection cavity causes the first and second blade modules to be forced together. A pre-tensioned joint may be established between the first and second blade modules.

The free ends of the first and/or second inserts may have fir tree profiles. The profiled contours may therefore be fir tree profiles. The first and/or second end of the connecting element may have a fir tree profile. The fir tree profiles may have a single set of branches. Alternatively, the fir tree profiles may have multiple sets of branches. The connecting element may be a plate element with two opposing ends which have mushroom like cross sections.

The at least one connecting element may comprise an intermediate portion extending between the first and second profiled ends. Tool access spaces may be defined between the intermediate portion of the connecting element and the free ends of the inserts when the blade modules are connected together.

The at least one connecting element may be configured to be secured to one or more retaining elements associated with one or more of the inserts. The or each retaining element may comprise a bridge that extends between adjacent first inserts or between adjacent second inserts. Additionally or alternatively, the or each retaining element may comprise a bridge that extends between adjacent pairs of abutting inserts. The one or more retaining elements may be elastically deformable and may be configured to exert a force on the connecting element that pulls the connecting element deeper into mesh with the inserts.

The fixed ends of the first inserts may be embedded in a spar structure of the first blade module. The fixed ends of the second inserts may be embedded in a spar structure of the second blade module. The spar structure of the first blade module may be integrated with an outer shell of the first blade module. The spar structure of the second blade module may be integrated with an outer shell of the second blade module.

In a second aspect of the invention there is provided a method of connecting first and second blade modules of a modular wind turbine blade. The method comprises providing first and second blade modules. The first blade module comprises a plurality of mutually spaced first inserts each having a fixed end integrated with a connection end of the first blade module. The first inserts each have a free end projecting from the connection end of the first blade module. The free ends have a profiled contour. The second blade module comprises a plurality of mutually spaced second inserts each having a fixed end integrated with a connection end of the second blade module. The second inserts each have a free end projecting from the connection end of the second blade module. The free ends have a profiled contour. The method further comprises arranging the first and second blade modules end to end such that the free ends of the first inserts abut the free ends of the second inserts, and providing at least one connecting element having a profiled first end and a profiled second end. The method further comprises inserting the at least one connecting element into a respective connection cavity defined between the profiled contours of adjacent pairs of abutting inserts. The profiled first end of the connecting element intermeshes with the profiled contours of adjacent first inserts. The profiled second end of the connecting element intermeshes with the profiled contours of adjacent second inserts. The at least one connecting element thereby connects the first and second blade modules together.

The inserts and the connecting element may be configured such that inserting a connecting element into a respective connection cavity causes the first and second blade modules to be forced together. A pre-tensioned joint may be established between the first and second blade modules.

Optional and advantageous features described above in relation to any one aspect of the invention are equally applicable to the other aspects of the invention. Repetition of such features is avoided purely for reasons of conciseness.

Brief description of the drawings

Embodiments of the present invention will now be described by way of non-limiting example only, with reference to the accompanying figures, in which:

Figure 1 is a schematic perspective view of a modern utility-scale wind turbine comprising modular wind turbine blades;

Figure 2 is a schematic plan view of a modular wind turbine blade comprising first and second blade modules; Figure 3 is a schematic perspective view of a plurality of inserts embedded in a spar cap of a blade module;

Figure 4 is a schematic plan view of an interface between first and second blade modules connected together by connecting elements to form a modular blade;

Figure 5 is a schematic cross-sectional view taken along line A-A in Figure 4; Figure 6a is a schematic cross-sectional view along line B-B in Figure 4 showing an example where a connecting element is optionally secured to a retaining element spanning adjacent inserts; Figure 6b shows an elastically deformed retaining element; and

Figure 7 shows an interface between first and second blade modules connected together to form a modular blade in another example.

Detailed Description

Figure 1 is a schematic perspective view of a modern utility-scale wind turbine 10. The wind turbine 10 comprises a tower 12 supporting a nacelle 14 to which a rotor 16 is mounted. The rotor 16 comprises a plurality of radially extending modular wind turbine blades 18 which are attached at their respective root ends 20 to a central hub 22. In this example, the rotor 16 comprises three blades 18, but in other examples the rotor 16 may have any number of blades 18. The modular blades 18 may be assembled at a wind farm site to facilitate easier transportation of large components.

In this example the blades 18 each comprise first and second blade modules 24a, 24b, though more than two modules 24 per blade 18 may be used in other examples. As shown in Figure 1 , in this example the first blade module 24a is an inboard module, and comprises a root end 20 of the blade 18, and the second blade module 24b is an outboard module, and comprises a tip end 26 of the blade 18. In other examples, where the modular blade 18 comprises more than two blade modules 24, the first and second blade modules 24a, 24b may not necessarily comprise the root end 20 or tip end 26 of the blade 18.

The first and second blade modules 24a, 24b are connected end to end at an interface 28. A connection end 30a, 30b of each blade module 24a, 24b is therefore defined as the respective end of that module which connects to the other module.

A modular blade 18 is shown schematically in plan view in Figure 2. The blade 18 extends longitudinally from the root end 20 to the tip end 26 in a spanwise direction (S). A longitudinal axis of the blade 18 is denoted by line L in Figure 2. The blade 18 extends between a leading edge 32 and a trailing edge 34 in a chordwise direction (C), substantially perpendicular to the spanwise direction (S).

The blade 18 is shown in Figure 2 prior to connection of the first and second blade modules 24a, 24b. Each of the blade modules 24a, 24b comprises an outer shell 36a, 36b. The outer shells 36 are preferably made from a composite material, for example glass fibre reinforced plastic (GFRP). In this example, each blade module 24a, 24b comprises spar caps 38a, 38b which extend longitudinally in the spanwise direction (S) to absorb bending loads along the blade 18. The spar caps 38 may be formed of a composite material such as carbon fibre reinforced plastic (CFRP). The spar caps 38 form part of a reinforcing spar structure of the blade 18 and are arranged on each of a windward side 40 and leeward side (not shown) of each blade module 24. In preferred examples, the spar caps 38a, 38b of the first and second blade modules 24a, 24b are integrated with the respective outer shell 36a, 36b of said first and second blade module 24a, 24b. For example, the spar caps 38 may be embedded between layers of fibrous reinforcing material when forming the composite shells 36 of the blade modules 24.

The first blade module 24a comprises a plurality of first inserts 42a which extend longitudinally in the spanwise direction (S) from the connection end 30a of the first blade module 24a. Similarly, the second blade module 24b comprises a plurality of second inserts 42b which extend longitudinally in the spanwise direction (S) from the connection end 30b of the second blade module 24b. The first and second inserts 42a, 42b are configured to enable connection of the first and second blade modules 24a, 24b. In this example, and as shown more clearly in Figure 3, the first and second inserts 42a, 42b are embedded in the spar caps 38a, 38b of the reinforcing spar structures of the first and second blade modules 24a, 24b.

Figure 3 shows a plurality of inserts 42 embedded in a spar cap 38 at the connection end 30 of a blade module 24. The spar cap 38 shown in Figure 3 may be a spar cap 38a or 38b of the first blade module 24a or the second blade module 24b respectively. It will be understood that the configuration of the inserts 42 is substantially the same for both the first and second blade modules 24a, 24b in this example. The outer shell 36 of the blade module 24 is not shown in Figure 3 for clarity.

Referring to Figure 3, the inserts 42 each comprise a fixed end 44 and a free end 46. The fixed end 44 of each insert 42 is integrated with the connection end 30 of the blade module 24. In this example the fixed end 44 of each insert 42 is embedded in the spar cap 38 as indicated by the dashed lines. The inserts 42 are mutually spaced in the chordwise direction (C) such that a chordwise separation X between adjacent inserts 42 is substantially uniform.

The free end 46 of each insert 42 comprises a profiled contour 48. In this example, the free end 46 of each insert has a so-called “fir tree” profile, which comprises branches 50 extending from a central portion 52 of the insert 42. As shown in Figure 3, each insert 42 in this example comprises a single set of two branches 50, with one branch extending in the chordwise direction (C) on each opposing side of the central portion 52. The branches 50 define contact surfaces 54 which are configured to engage with corresponding contact surfaces 56 of a connecting element 58 (as shown in Figure 4).

The free end 46 of each insert 42 further comprises an end surface 60. In this example the end surface 60 of each insert 42 is a substantially flat planar surface, which is substantially perpendicular to the longitudinal axis L. It is conceivable that in some examples the end surface 60 of an insert 42 could be inclined relative to the longitudinal axis L. In this example the end surfaces 60 of the respective inserts 42 are substantially co-planar.

Figure 4 is a schematic plan view of a portion of the interface 28 between the first and second blade modules 24a, 24b when the blade modules are connected together to form the modular blade 18.

When the first and second blade modules 24a, 24b are connected, the free ends 46a of the first inserts 42a abut the free ends 46b of the second inserts 42b. In this example, the respective end surfaces 60a, 60b of the first and second inserts 42a, 42b are in direct contact. However, in other examples, a plate or other member could be provided in between the opposed end surfaces 60a, 60b, in which case said end surfaces would be in indirect contact. Accordingly, the term ‘abut’ as used herein should be interpreted to include both direct and indirect contact between opposed inserts 42a, 42b.

When the free ends 46a, 46b of the first and second inserts 42a, 42b abut, the profiled contours 48 of adjacent pairs of abutting inserts 42 define connection cavities 62 therebetween. The first and second blade modules 24a, 24b are connected together by connecting elements 58 which are inserted into these connection cavities 62.

Each connecting element 58 comprises a first end 64a and a second end 64b, which are joined together by an intermediate portion 66. The intermediate portion 66 extends longitudinally in the spanwise direction (S) between the first and second ends 64a, 64b and forms a cross-bar which fixes the first and second ends 64a, 64b relative to one another. The connecting element is a plate element and extends into the plane of the page in Figure 4. The first end 64a of each connecting element 58 comprises a profile 68a configured to intermesh with the profiled contours 48a of adjacent first inserts 42a of the first blade module 24a. Similarly, the second end 64b of each connecting element 58 comprises a profile 68b configured to intermesh with the profiled contours 48b of adjacent second inserts 42b of the second blade module 24b. In this example the first and second ends 64a, 64b of the connecting elements 58 are configured in substantially the same manner. As shown in Figure 4, the first and second ends 64a, 64b of the connecting elements 58 have a mushroom like cross section in this example.

The first and second ends 64a, 64b of the connecting elements 58 comprise contact surfaces 56a, 56b configured to engage with the contact surfaces 54a and 54b of the first and second inserts 24a, 24b. The contact surfaces 56a of the first end 64a of each connecting element 58 are configured in opposed relation to the contact surfaces 56b of the second end 64b of the connecting element 58. As such, each connecting element 58 comprises two pairs of mutually-opposed contact surfaces 56.

Each connecting element 58 in this example further comprises two elongate studs 70 which extend substantially perpendicular to the longitudinal axis L of the blade 18. As will be described in more detail later with reference to Figures 6a and 6b, the studs 70 may be coupled to a retaining element 72 to secure the connecting elements 58 in the connection cavities 62 during use.

To connect the first and second blade modules 24a, 24b together, the blade modules are arranged end to end such that the first inserts 42a are aligned with the corresponding second inserts 42b as shown in Figure 4. The inserts 42a, 42b are brought into abutment and connecting elements 58 are inserted into the connection cavities 62. The connecting elements 58 are inserted in an insertion direction (/) which is transverse to both the spanwise (S) and chordwise (C) directions. In this example the insertion direction (/) is substantially perpendicular to the longitudinal axis L of the blade 18, and as such is substantially perpendicular to the plane of the page in Figure 4.

On insertion of a connecting element 58 into a connection cavity 62, the profiled first end 64a of the connecting element 58 intermeshes with the free ends 46a of adjacent first inserts 42a. The second end 64b of the connecting element 58 intermeshes with the free ends 46b of adjacent second inserts 42b. Once inserted, the connecting element 58 spans the interface 28 between the first and second blade modules 24a, 24b. Access spaces 74 may be defined in the connection cavity 62 between the intermediate portion 66 of a connecting element 58 and the profiled contours 48 of adjacent pairs of abutting inserts 42. In some examples, an insertion tool (not shown) may be used to insert and/or extract connecting elements 58 from the connection cavity 62. The access spaces 74 enable such a tool to interface with a connecting element 58 even when the connecting element 58 is partially or wholly inserted in the connection cavity 62.

In some advantageous examples, the contact surfaces 54a, 54b of the inserts 42a, 42b may be inclined relative to the longitudinal axis L of the blade 18, i.e. the contact surfaces 54a, 54b may be non-perpendicular relative to the longitudinal axis L. Alternatively, or preferably additionally, the contact surfaces 56a, 56b of the connecting elements 58 may also be inclined. As will now be described in more detail with reference to Figure 5, a pre-tensioned joint may therefore be established between the first and second blade modules 24a, 24b in such an example.

Figure 5 shows a cross-sectional view through a connection cavity 62, along the line A-A indicated in Figure 4. For clarity, the connection cavity 62 in Figure 5 is shown prior to insertion of a connecting element 58. As described above, the connection cavity 62 is defined by adjacent pairs of abutting first and second inserts 42a, 42b which each have one or more contact surfaces 54a, 54b. In this example the contact surfaces 54a, 54b of the first and second inserts 42a, 42b are inclined relative to the longitudinal axis L of the blade 18.

The contact surfaces 54 of the inserts 42 are inclined such that contact surfaces 54a, 54b of the first and second inserts 42a, 42b are mutually divergent along the insertion direction (/) when the inserts 42a, 42b are in abutment as shown in Figure 5. A spanwise separation Y is defined between the contact surfaces 54a of the first insert 42a and the contact surfaces 54b of the second insert 42b. The spanwise separation Y therefore changes going from a first side 76 of the inserts 42 to a second side 78 in the insertion direction (I). In this example, the spanwise separation Y increases going from the first side 76 to the second side 78. In this example, the first side 76 is an exterior-facing side and the second side 78 of the inserts 42 faces an interior of the modular blade 18.

The contact surfaces 56a, 56b at the first and second ends 64a, 64b of the connecting element 58 are also mutually inclined as shown in Figure 5. In this example, the opposed contact surfaces 56a, 56b are mutually divergent. A spanwise separation Z is defined between the opposed contact surfaces 56a and 56b. The spanwise separation Z increases going from a first side 80 of the connecting element 58 to a second side 82 in the insertion direction (/).

As mentioned previously, the first and second blade modules 24a, 24b are connected together by inserting a connecting element 58 into the connection cavity 62 in the insertion direction (/). In this example, the connecting element 58 is inserted from the first (exterior-facing) side 76 of the inserts 42. The connecting element contact surfaces 56a, 56b engage the contact surfaces 54a, 54b of the first and second inserts 42a, 42b. The mutual divergence of the insert contact surfaces 54a, 54b, in conjunction with the mutual divergence of the connecting element contact surfaces 56a, 56b, causes the first and second blade modules 24a, 24b to be pulled together in the spanwise direction (S) when the connecting element 58 is moved along the insert contact surfaces 54 in the insertion direction (/).

With the free ends 46a, 46b of the first and second inserts 42a, 42b in abutment, no further spanwise movement of the inserts 42a, 42b or blade modules 24a, 24b is possible. Further, the connecting element contact surfaces 56a, 56b are maintained in fixed relation to one another because the first and second ends 64a, 64b of said connecting element 58 are joined by the intermediate portion 66. The spanwise separation Z between the connecting element contact surfaces 56a, 56b is therefore also fixed.

As the connecting element 58 is pressed or pulled into the connection cavity 62, the connecting element contact surfaces 56a, 56b run along the mutually divergent contact surfaces 54a, 54b of the first and second inserts 42a, 42b. Forcing a connecting element 58 further into the connection cavity 62 in the insertion direction (/) results in tensile loading of said connecting element 58, because the spanwise separation Y between the mutually divergent insert contact surfaces 54a, 54b increases going from the first side 76 of the inserts 42 to the second side 78 in the insertion direction (/). The first and second blade modules 24a, 24b are therefore forced together and a pre-tensioned connection is established between said blade modules 24. In some examples, the previously mentioned insertion tool may be used to force the connecting elements 58 further into mesh with the free ends 46a, 46b of the first and second inserts 42a, 42b.

In this example, the inserts 42a, 42b are embedded in the spar caps 38a, 38b and the pre-tensioned connection is therefore formed between the reinforcing spar structures of the first and second blade modules 24a, 24b. Embedding the inserts 42 in the spar caps 38 of each module 24 facilitates a strong joint between the main load bearing elements of the blade modules 24 and enables a large amount of loading to be transferred across the interface 28 between modules in a relatively small area. Further, in examples where the inserts 42 and connecting elements 58 are formed of a high-strength material such as steel, the size of such components can be reduced on account of the load-bearing properties of their materials. A relatively compact connection solution is thereby achieved without adding considerable weight to the modular blade 18.

In use, a modular blade 18 may flex, due for example to varied wind conditions or the effect of gravity at different positions during rotation of the rotor 16. However, because the connecting elements 58 are pre-tensioned, even when flexing of the blade 18 causes the loading on the connecting elements 58 to vary, the elements 58 remain loaded in tension. Further, because the connecting elements 58 primarily undergo tensile loading, and do not particularly experience torsional loading or bending moments, the elements 58 can be reasonably small in size relative to the size of the blade 18.

Each connecting element 58 in this example is secured in a respective connection cavity 62 by a retaining element 72 which spans said connection cavity 62 as will now be described with reference to Figures 6a and 6b.

Referring to Figure 6a, this shows a cross-sectional view at the interface between first and second inserts 42a, 42b taken along the line B-B in Figure 4. For clarity, only two adjacent inserts 42 are shown in Figure 6a, however, it will be appreciated that in preferred examples there are more than two chordwise adjacent inserts 42 embedded in the spar caps 38a, 38b of the first and second blade module 24a, 24b (as shown in Figure 4 for example).

The retaining element 72 in this example comprises a bridge structure which spans the connection cavity 62 between the two adjacent inserts 42. In this example, the retaining element 72 is arranged on the second side 78 of the inserts 42. The retaining element 72 has a main beam 84 and two support legs 86 which extend from the main beam 84 substantially perpendicular to the longitudinal axis L of the blade 18. The support legs 86 bear against a side surface 88 on the second side 78 of the inserts 42. In this example the side surfaces 88 are interior-facing surfaces. Each support leg 86 bears against an insert 42, or against a pair of abutting inserts 42a, 42b such that the retaining element 72 spans the connection cavity 62. The retaining element 72 comprises a through-hole 90 in the main beam 84 configured to fit over the elongate stud 70 of the connecting element 58. The elongate stud 70 projects from the connecting element 58 perpendicular to the longitudinal axis L of the blade 18. Further, the elongate stud 70 comprises an external thread 92, which in this example is an M10 bolt thread.

To secure the connecting element 58 in place, the connecting element 58 is inserted into the connection cavity 62 from the first (exterior-facing) side 76 of the inserts 42 (as shown in Figure 6), and a retaining element 72 is arranged on the second (interior facing) side 78 of the inserts 42. The retaining element 72 in this example is therefore arranged on the side of the inserts 42 opposite to that from which the connecting element 58 was inserted into the connection cavity 62.

The retaining element 72 is arranged such that the threaded stud 70 extends through the hole 90 in the main beam 84. A nut 94 is then fastened onto the threaded stud 70. Fastening the nut 94 causes the connecting element 58 to be pulled in the insertion direction (/) and further into mesh with the free ends 46a, 46b of the first and second inserts 42a, 42b, pulling the blade modules 24a, 24b together in the spanwise direction (S).

In this example, the main beam 84 of the retaining element 72 deforms elastically as the nut 94 is fastened further onto the threaded stud 70 as shown in Figure 6b. With the nut 94 fastened in position, securing the connecting element 58 in the connection cavity 62, the elastically deformable retaining element 72 is pre-loaded and exerts a pulling force perpendicular to the longitudinal axis L, in the insertion direction (/). Even if the retaining element 72 unloads slightly from its loaded state, the pre-load on the retaining element 72 ensures that said retaining element 72 still exerts a force on the connecting element 58 to secure it in the connection cavity 62. The pre-loaded retaining element 72 therefore ensures that the ends 64a, 64b of the connecting element 58 are always pulled into mesh with the free ends 46a, 46b of the first and second inserts 42a, 42b.

Figure 7 shows an alternative configuration for connecting the first and second blade modules 24a, 24b to form a modular blade 18. The free ends 46a, 46b of the first and second inserts 42a, 42b in this example again comprise a fir tree profile. In this example the fir tree profiles comprise two sets of branches 50 extending in the chordwise direction (C) on each side of the inserts 42a, 42b. Each of the branches 50 of the inserts 42 in this example defines a contact surface 54. The connecting elements 58 also comprise a fir tree profile in this example. The connecting elements 58 have two sets of branches 96 at each of their first and second ends 64a, 64b to intermesh with the fir tree profiles of adjacent first inserts 42a and adjacent second inserts 42b respectively. The branches 96 of the connecting elements 58 define contact surfaces 56 which are configured to engage with the insert contact surfaces 54.

In this example the contact surfaces 54 of the inserts are inclined relative to the longitudinal axis L of the blade 18 as described above with reference to the example of Figure 5. Similarly, the contact surfaces 56 of the connecting elements 58 are also inclined. The connecting elements 58 are used to connect first and second blade modules 24a, 24b together as described above with reference to Figures 4 and 5. The connecting elements 58 are therefore inserted into a connection cavity 62 in the insertion direction (/), which is transverse to both the spanwise direction (S) and chordwise direction (C). Similarly, the insertion direction (/) in this example is substantially perpendicular to the longitudinal axis L of the blade 18 and extends perpendicular to the plane of the page in Figure 7. A pre-tensioned connection is established between the blade modules 24a, 24b when the connecting elements 58 are inserted into the connection cavities 62 due to the inclined contact surfaces 54 and 56.

The inserts 42 and connecting elements 58 shown in Figure 7 comprise relatively complex geometry and may therefore be more difficult to manufacture than those of the examples previously described. For example, the connecting elements 58 in Figures 3 to 6 only comprise a single set of branches at each of the first and second ends of said connecting element 58, and said branches define two pairs of mutually opposed contact surfaces 56. However, in some examples the two sets of branches 50, 96 may provide a stronger connection between blade modules 24a, 24b as a result of the increased contact surface area between the inserts 42 and connecting elements 58. In other examples it is therefore conceivable that the inserts 42 and connecting elements 58 may have any number of sets of branches 50, 96.

In yet further examples, it is conceivable that an insert 42 may comprise branches 50 on one side of the insert 42 only, for example where an insert 42 has only one neighbouring insert 42 in the chordwise direction (C). The branches 50 of such an insert 42 may extend from a central portion 52 of said insert 42 on the side thereof facing the neighbouring insert 42, with the profile 48 of the free end 46 forming part of a connection cavity 62. In some further examples, the profiled contours 48a, 48b of the first and second inserts 42a, 42b may not necessarily be the same. That is to say, the free ends 46a of the first inserts 42a in some examples may comprise a first profiled contour 48a and the free ends 46b of the second inserts 42b may comprise a second profiled contour 48b, wherein the first and second profiled contours 48a, 48b are different. A connecting element 58 in such an example may therefore comprise first and second ends 64a, 64b having a different profile 68a, 68b, where each end 64a, 64b is configured to intermesh with the free ends 46a or 46b of either adjacent first inserts 42a or adjacent second inserts 42b.

In preferred examples however, the free ends 46a, 46b of the first and second inserts 42a, 42b each comprise the same profile 48, as illustrated throughout the accompanying figures. The connecting element 58 in such an example has the same profile 68 at the first and second ends 64a, 64b, and can be oriented either way around in a connection cavity 62 when connecting the blade modules 24a, 24b. For example the first end 64a of the connecting element 58 may intermesh with either adjacent first inserts 42a or with adjacent second inserts 42b since the profiled contours 48a, 48b of the first and second inserts 42a, 42b are the same in such an example.

In some examples the inserts 42 may not comprise a fir tree profile as described throughout and depicted in the figures. The inserts 42 may instead comprise a different profile 48 which similarly serves to intermesh with the first and second ends 64a, 64b of a connecting element 58 to connect the blade modules 24a, 24b together. However, a fir tree profile, as depicted in Figures 4 and 7 for example, is advantageous because said profile provides a central portion 52 having a cross sectional area sufficient to transfer the loads involved in connecting blade modules 24 together, whilst also providing branches 50 to define the contact surfaces 54 and providing access spaces 74 between the contours 48 and the connecting elements 58.

In preferred examples, the connecting element contact surfaces 56a, 56b are configured to be substantially parallel to the contact surfaces 54a, 54b of the respective first and second inserts 42a, 42b when connecting the blade modules 24a, 24b together (as shown in Figure 5 for example). This enables a simple insertion of the connecting element 58 into the connection cavity 62, allowing the connecting element contact surfaces 56 to move smoothly along the contact surfaces 54 of the inserts 42. Further, an increased contact area between the connecting element 58 and inserts 42 is provided where the connecting element contact surfaces 56 are substantially parallel with the contact surfaces 54 of the inserts 42, in comparison to examples where said contact surfaces may not be parallel.

Further, the contact surfaces 56a of chordwise adjacent first inserts 42a are preferably co-planar to allow a connecting element 58 to be slid into the connection cavity 62. Similarly, in preferred examples the contact surfaces 56b of chordwise adjacent second inserts 42b are also co-planar.

In some of the previously described examples, such as that shown in Figure 5, each of the contact surfaces 54a, 54b and 56a, 56b of the inserts 42 and connecting elements 58 is inclined. However, in some further examples, one or more of the contact surfaces 54a, 54b, 56a, 56b may not be inclined. Only at least one of the contact surfaces 54a, 54b, 56a, 56b needs to be inclined in order for the modules 24a, 24b to be pulled together in the spanwise direction (S), and to establish a pre-tensioned connection between said modules 24a, 24b, when inserting a connecting element 58 in the insertion direction (/).

In preferred examples the insertion direction (/) is out-of-plane relative to at least one of the insert contact surfaces 54a, 54b or the connecting element contact surfaces 56a, 56b, so that inserting a connecting element 58 in the insertion direction (/) causes the first and second blade modules 24a, 24b to be pulled together in the spanwise direction (S), and to establish a pre-tensioned connection between said modules 24a, 24b. That is to say, at least one of the connecting element 58 or a pair of abutting inserts 42a, 42b comprises mutually divergent contact surfaces 54a, 54b and/or 56a, 56b.

It will be appreciated that the invention is not limited to a particular number of inserts 42 embedded in the connection end 30 of a blade module 24. Further, it is conceivable that in some examples the first and second blade modules 24a, 24b may comprise inserts 42a, 42b embedded in their respective composite outer shells 36a, 36b instead of or in addition to inserts 42a, 42b embedded in the spar caps 38a, 38b of their reinforcing spar structures as described herein. In yet further examples, the inserts 42a, 42b may be embedded in load bearing elements at the trailing edge 34 of each blade module 24a, 24b. In such examples, the inserts 42 and connecting elements 58 as described herein may be used to connect trailing edge stringers of first and second blade modules 24a, 24b.

The connecting elements 58 are preferably metal components. In advantageous examples the connecting elements 58 are formed of a corrosion resistant material with a high yield strength such as a stainless steel alloy. In some examples the connecting elements 58 and/or their contact surfaces 56a, 56b may be hardened. In examples where the connecting elements 58 are made from steel, martensitic hardening mechanisms such as quenching and tempering are preferred.

The retaining element 72 described with reference to Figures 6a and 6b is provided merely as one example of a retaining element 72. In other examples, a retaining element 72 may comprise more than two support legs 86 extending from a main beam 84 perpendicular to the longitudinal axis L. Such a retaining element 72 may for example span a plurality of connection cavities 62 and may be used to secure a plurality of connecting elements 58 in said connection cavities 62.

In other examples the connecting element 58 may be inserted from the second (interior facing) side 78 of the inserts 42 and the retaining element 72 may be arranged on the first (exterior-facing) side 76 of the inserts 42. In each example however, where a retaining element 72 as described herein is used to secure the connecting element 58, said retaining element 58 should be arranged on the opposite side of the inserts 42 to that from which the connecting element 58 is inserted. This ensures that the retaining element 72 pulls the connecting element 58 into mesh with the free ends 46a, 46b of the first and second inserts 24a, 24b.

In the examples discussed above, the plurality of inserts 42 are embedded in the spar cap 38. However, instead of embedding the inserts 42 directly in the spar caps 38, the inserts may be provided in a separate slab of material, such as glass or carbon fibre reinforced plastic, and this separate slab may then be integrated with the spar caps 38. Such “slabs” form part of the spar structure.

Finally, in some examples, the modular blade 18 may comprise elongate shear pins 98 (indicated in dashed lines in Figure 4) to help align first and corresponding second inserts 42a, 42b. The shear pins 98 may also restrict shear movement of the first and second inserts 42a, 42b relative to one another in use. The shear pins 98 may be located in holes 100a, 100b provided in the end surfaces 60a, 60b of first and corresponding second inserts 42a, 42b. In use, a shear pin 98 may be arranged in a hole 100a of a first insert 42a such that the shear pin 98 extends from the end surface 60 of the insert 42a in the spanwise direction (S). When the first and second blade modules 24a, 24b are brought together, a hole 100b in the corresponding second insert 42b may be aligned with the spanwise extending shear pin 98. When the free ends 46a, 46b of the first and second inserts 42a, 42b are brought into abutment, the shear pin 98 may be located at least partially in each hole 100a, 100b of corresponding first and second inserts 42a, 42b, thereby aligning first and second inserts with one another. The modular blade 18 in such an example preferably comprises shear pins 98 located in holes 100 of at least the chordwise outermost pairs of abutting first and second inserts 42a, 42b. Alternatively, a modular blade 18 may comprise shear pins 98 in holes 100 provided in each pair of abutting first and second inserts 42a, 42b. It will be appreciated that features described in relation to the various examples above may be readily combined with features described with reference to different examples without departing from the scope of the invention as defined in the appended claims.

Further, it will be appreciated that the above description and accompanying figures are provided merely as an example. Many alternatives to the modular blade and connection method described above are therefore possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A modular wind turbine blade (18) comprising: first and second blade modules (24a, 24b) configured for connection end to end; a plurality of mutually spaced first inserts (42a) each having a fixed end (44) integrated with a connection end of the first blade module and a free end (46) projecting from the connection end of the first blade module, the free ends having a profiled contour (48); a plurality of mutually spaced second inserts (42b) each having a fixed end (44) integrated with the connection end of the second blade module and a free end projecting (46) from the connection end of the second blade module, the free ends having a profiled contour (48); wherein the free ends of the first inserts abut the free ends of the second inserts when the first and second blade modules are arranged end to end, and one or more connection cavities (62) are defined between the profiled contours of adjacent pairs of abutting inserts, the modular wind turbine blade further comprising: at least one connecting element (58) configured for insertion into a respective connection cavity (62) to connect the first and second blade modules together, the at least one connecting element having a first end (64a) and a second end (64b), the first end having a profile configured to intermesh with the profiled contours of adjacent first inserts, and the second end having a profile configured to intermesh with the profiled contours of adjacent second inserts.

2. The modular wind turbine blade of Claim 1 , wherein a plurality of connection cavities are defined respectively between the profiled contours of adjacent pairs of abutting inserts, and a respective connecting element is received in each connection cavity.

3. The modular wind turbine blade of Claim 1 or Claim 2, wherein the free ends of the inserts define contact surfaces for engaging with corresponding contact surfaces of a respective connecting element, wherein the respective contact surfaces are angled such that inserting a connecting element into a connection cavity causes the first and second blade modules to be forced together such that a pre-tensioned joint is established between the first and second blade modules.

4. The modular wind turbine blade of any preceding claim, wherein the free ends of the first and/or second inserts have fir tree profiles.

5. The modular wind turbine blade of any preceding claim, wherein the first and/or second end of the or each connecting element has a fir tree profile.

6. The modular wind turbine blade of Claim 4 or Claim 5, wherein the fir tree profiles have a single set of branches.

7. The modular wind turbine blade of any preceding claim, wherein the or each connecting element is a plate element with two opposing ends which have mushroom like cross sections.

8. The modular wind turbine blade of any preceding claim, wherein the or each connecting element comprises an intermediate portion extending between the first and second profiled ends, and wherein tool access spaces are defined between the intermediate portion of a respective connecting element and the free ends of the inserts when the blade modules are connected together.

9. The modular wind turbine blade of any preceding claim, wherein the at least one connecting element is configured to be secured to one or more retaining elements associated with one or more of the inserts.

10. The modular wind turbine blade of Claim 9, wherein the or each retaining element comprises a bridge that extends between adjacent first inserts and/or between adjacent second inserts.

11. The modular wind turbine blade of Claim 9 or Claim 10, wherein the or each retaining element is elastically deformable and is configured to exert a force on a respective connecting element that pulls the connecting element deeper into mesh with the inserts.

12. The modular wind turbine blade of any preceding claim, wherein the fixed ends of the first inserts are embedded in a spar structure of the first blade module, and the fixed ends of the second inserts are embedded in a spar structure of the second blade module.

13. The modular wind turbine blade of Claim 12, wherein the spar structure of the first blade module is integrated with an outer shell of the first blade module, and wherein the spar structure of the second blade module is integrated with an outer shell of the second blade module.

14. A method of connecting first and second blade modules (24a, 24b) of a modular wind turbine blade (18), the method comprising: providing first and second blade modules (24a, 24b), the first blade module comprising a plurality of mutually spaced first inserts (42a) each having a fixed end (44) integrated with a connection end of the first blade module and a free end (46) projecting from the connection end of the first blade module, the free ends having a profiled contour (48), and the second blade module comprising a plurality of mutually spaced second inserts (42b) each having a fixed end (44) integrated with a connection end of the second blade module and a free end (46) projecting from the connection end of the second blade module, the free ends having a profiled contour (48); arranging the first and second blade modules (24a, 24b) end to end such that the free ends (46) of the first inserts (42a) abut the free ends of the second inserts (42b), providing at least one connecting element (58) having a profiled first end (64a) and a profiled second end (64b); and inserting the at least one connecting element into a respective connection cavity (62) defined between the profiled contours (48) of adjacent pairs of abutting inserts, (42a, 42b) such that the profiled first end of the connecting element intermeshes with the profiled contours of adjacent first inserts, and the profiled second end of the connecting element intermeshes with the profiled contours of adjacent second inserts, the at least one connecting element thereby connecting the first and second blade modules together.

15. The method of Claim 14, wherein the inserts and the connecting element are configured such that inserting a connecting element into a respective connection cavity causes the first and second blade modules to be forced together and a pre-tensioned joint to be established between the first and second blade modules.