MODULAR WIND TURBINE BLADE

Abstract

According to the present invention there is provided a modular wind turbine blade comprising first and second blade modules connectable together to form at least part of the wind turbine blade, each blade module comprising an outer shell defining a pressure side and a suction side of the wind turbine blade. The first blade module comprises a first spar cap, and the second blade module comprising a second spar cap. The first spar cap has a tapered end portion in which the thickness of the first spar cap decreases towards the end of the first spar cap. The modular wind turbine blade further comprises an elongate connecting element for connecting the first and second blade modules together. The connecting element has a first tapered end portion in which the thickness of the connecting element decreases towards a first end of the connecting element. The first tapered end portion is configured for bonding to the tapered end portion of the first spar cap. The first spar cap has an inner surface and an outer surface, the thickness being defined between the inner surface and the outer surface. The first spar cap comprises (i) an intermediate thickness band; (ii) an inner thickness band between the intermediate thickness band and the inner surface; and (iii) an outer thickness band between the intermediate thickness band and the outer surface. Each of the thickness bands have a tapered end within the tapered end portion of the first spar cap. The connecting element has an inner surface and an outer surface, the thickness of the connecting element being defined between the inner surface and the outer surface. The connecting element comprises (i) an intermediate thickness band; (ii) an inner thickness band between the intermediate thickness band and the inner surface; and (iii) an outer thickness band between the intermediate thickness band and the outer surface. Each of the thickness bands has a tapered end within the first tapered end portion of the connecting element. The tapered end of the inner thickness band and/or the tapered end of the outer thickness band of the first spar cap has a lower rate of taper than the tapered end of the intermediate thickness band of the first spar cap. Additionally or alternatively, the tapered end of the inner thickness band and/or the tapered end of the outer thickness band of the connecting element has a lower rate of taper than the tapered end of the intermediate thickness band of the connecting element.

Claims

1. A modular wind turbine blade comprising: first and second blade modules connectable together to form at least part of the wind turbine blade; each blade module comprising an outer shell defining a pressure side and a suction side of the wind turbine blade, the first blade module comprising a first spar cap, and the second blade module comprising a second spar cap; the first spar cap having a tapered end portion in which the thickness of the first spar cap decreases towards the end of the first spar cap; an elongate connecting element for connecting the first and second blade modules together, the connecting element having a first tapered end portion in which the thickness of the connecting element decreases towards a first end of the connecting element, the first tapered end portion being configured for bonding to the tapered end portion of the first spar cap; the first spar cap having an inner surface and an outer surface, the thickness being defined between the inner surface and the outer surface, the first spar cap comprising (i) an intermediate thickness band; (ii) an inner thickness band between the intermediate thickness band and the inner surface; and (iii) an outer thickness band between the intermediate thickness band and the outer surface, each of the thickness bands having a tapered end within the tapered end portion of the first spar cap; the connecting element having an inner surface and an outer surface, the thickness of the connecting element being defined between the inner surface and the outer surface, the connecting element comprising (i) an intermediate thickness band; (ii) an inner thickness band between the intermediate thickness band and the inner surface; and (iii) an outer thickness band between the intermediate thickness band and the outer surface, each of the thickness bands having a tapered end within the first tapered end portion of the connecting element; wherein the tapered end of the inner thickness band and/or the tapered end of the outer thickness band of the first spar cap has a lower rate of taper than the tapered end of the intermediate thickness band of the first spar cap; and/or wherein the tapered end of the inner thickness band and/or the tapered end of the outer thickness band of the connecting element has a lower rate of taper than the tapered end of the intermediate thickness band of the connecting element.

2. The modular wind turbine blade of claim 1, wherein the connecting element comprises a tapered end portion of the second spar cap extending from the second blade module.

3. The modular wind turbine blade of claim 1, wherein the second spar cap has a tapered end portion, and wherein the connecting element is separate from the first and second blade modules and further comprises a second tapered end portion, the first and second tapered end portions of the connecting element being configured for bonding to the respective tapered end portions of the first and second spar caps.

4. The modular wind turbine blade of claim 1, wherein the inner and/or outer thickness band of the first spar cap each have a thickness of between 5% to 25% of the total thickness of the first spar cap, and the intermediate thickness band of the first spar cap has a thickness of between 50% to 90% of the total thickness of the first spar cap, and/or wherein the inner and/or outer thickness band of the connecting element each have a thickness of between 5% to 25% of the total thickness of the connecting element, and the intermediate thickness band of the connecting element has a thickness of between 50% to 90% of the total thickness of the connecting element.

5. The modular wind turbine blade of claim 1, wherein the first spar cap and/or the second spar cap and/or the connecting element comprise a stack of layers.

6. The modular wind turbine of claim 5, wherein the layers are pultrusions.

7. The modular wind turbine blade of claim 5, wherein the intermediate thickness band of the first spar cap comprises more layers than the inner thickness band of the first spar cap and/or more layers than the outer thickness band of the first spar cap, and/or wherein the intermediate thickness band of the connecting element comprises more layers than the inner thickness band of the connecting element and/or more layers than the outer thickness band of the connecting element.

8. The modular wind turbine blade of claim 5, wherein the inner thickness band of the first spar cap and/or the outer thickness band of the first spar cap comprises a single layer, and the intermediate portion of the first spar cap comprises a plurality of layers, and/or wherein the inner thickness band of the connecting element and/or the outer thickness band of the connecting element comprises a single layer, and the intermediate portion of the connecting element comprises a plurality of layers.

9. The modular wind turbine blade of claim 5, wherein the or each layer of the inner and/or outer thickness band of the first spar cap tapers over a longer spanwise length than each layer of the intermediate thickness band of the first spar cap, and/or wherein the or each layer of the inner and/or outer thickness band of the connecting element tapers over a longer spanwise length than each layer of the intermediate thickness band of the connecting element.

10. The modular wind turbine blade of claim 1, wherein the tapered end of the inner thickness band and/or the tapered end of the outer thickness band of the first spar cap defines a curved taper, and/or wherein the tapered end of the inner thickness band and/or the tapered end of the outer thickness band of the connecting element defines a curved taper.

11. The modular wind turbine blade of claim 1, wherein the tapered end of the inner thickness band of the first spar cap defines a curved taper that is curved in an opposite sense to a curved taper of the tapered end of the inner thickness band of the connecting element, and/or wherein the tapered end of the outer thickness band of the first spar cap defines a curved taper that is curved in an opposite sense to a curved taper of the tapered end of the outer thickness band of the connecting element.

12. The modular wind turbine blade of claim 1, wherein the tapered end of the intermediate thickness band of the first spar cap defines a linear taper, and/or wherein the tapered end of the intermediate thickness band of the connecting element defines a linear taper.

13. The modular wind turbine blade of claim 1, wherein the tapered ends of the inner, outer and intermediate thickness bands of the first spar cap together define a generally S-shaped or Z-shaped profile at the end of the first spar cap, and/or wherein the tapered ends of the inner, outer and intermediate thickness bands of the connecting element together define a generally S-shaped or Z-shaped profile at the first end of the connecting element.

14. The modular wind turbine blade of claim 1, further comprising an outer patch applied over an interface between the outer thickness band of the connecting element and the outer thickness band of the first spar cap, and/or an inner patch applied over an interface between the inner thickness band of the connecting element and the inner thickness band of the first spar cap.

15. The modular wind turbine blade of claim 14, wherein the outer patch and/or the inner patch comprises a stack of plies of fibrous reinforcing material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Examples of the present invention will now be described by way of non-limiting example only, with reference to the accompanying figures, in which:

[0043] FIG. 1 is a schematic exploded view of an example of modular wind turbine blade comprising a first blade module, a second blade module, and an elongate connecting element extending from the second blade module;

[0044] FIG. 2 is a schematic exploded view of an example of a modular wind turbine blade comprising a separate connecting element configured for connecting the first and second blade modules;

[0045] FIG. 3 is a schematic cross-sectional view of a tapered end portion of the connecting element and a tapered end portion of a spar cap of the first blade module; and

[0046] FIGS. 4a to 4d show schematic representations of a plurality of thickness progressions for examples of the tapered end portions of the connecting element and the spar cap.

[0047] FIG. 5 is a schematic cross-sectional view of a tapered end portion of the connecting element and a tapered end portion of a spar cap of the first blade module.

DETAILED DESCRIPTION

[0048] FIG. 1 is a schematic exploded view of a modular wind turbine blade 10. The blade 10 comprises a first blade module 12a and a second blade module 12b. The first and second blade modules 12a, 12b are connectable together to form at least part of the wind turbine blade 10. As such, the first and second blade modules 12a, 12b may be connected together at a joint 14.

[0049] In some examples, as shown in FIG. 1, the first blade module 12a may comprise a blade root 16 configured for connecting the blade 10 to a hub of a wind turbine (not shown), and the second blade module 12b may comprise a tip 18 of the wind turbine blade 10. In other examples (not shown), at least one of the first or second blade modules 12a, 12b may be an intermediate blade module and may not comprise a root 16 or tip 18 of the blade 10.

[0050] The first and second blade modules 12a, 12b each comprise an outer shell 20a, 20b defining a pressure side 22 and a suction side 24 of the wind turbine blade 10. The outer shell 20a, 20b of each blade module 12a, 12b extends in a spanwise direction (S) between the blade root 16 and the tip 18, and in a chordwise direction (C) between a leading edge 26 and a trailing edge 28.

[0051] The first blade module 12a comprises a first spar cap 30a, and the second blade module 12b comprises a second spar cap 30b. The spar caps 30a, 30b may form part of a structural spar that provides support to the outer shells 20a, 20b in use. The first and second spar caps 30a, 30b may be integrated with the respective outer shells 20a, 20b of the first and second blade modules 12a, 12b. Alternatively, the first and/or second spar cap 30a, 30b may be connected to an inner surface of the respective outer shell 20a, 20b of the first or second blade module 12a, 12b.

[0052] The first spar cap 30a has a tapered end portion 32a configured to facilitate an improved connection between the first and second blade modules 12a, 12b as will be described in more detail later with reference to FIG. 3. Accordingly, the thickness of the first spar cap 30a decreases towards the end 34 of the first spar cap 30a (shown in more detail in FIG. 3).

[0053] The modular wind turbine blade 10 further comprises an elongate connecting element 36 for connecting the first and second blade modules 12a, 12b. The connecting element 36 has a first tapered end portion 38a and the thickness of the connecting element 36 therefore decreases towards a first end 40 of the connecting element 36. The first tapered end portion 38a of the connecting element 36 is configured for bonding to the tapered end portion 32a of the first spar cap 30a. Further details of the first spar cap 30a and the elongate connecting element 36 will be described in more detail below with reference to FIGS. 3 and 4.

[0054] In some examples, the connecting element 36 may comprise a tapered end portion 32b of the second spar cap 30b. As shown in FIG. 1, the tapered end portion 32b of the second spar cap 30b may extend from the second blade module 12b. Complementary, the tapered end portion 32a of the first spar cap 30a may define a tapered recess 42a in the first blade module 12a. The first tapered end portion 38a of the connecting element 36 is preferably configured to fit within the tapered recess 42a of the first blade module 12a. Accordingly, the modular wind turbine blade 10 may comprise a single scarf joint 14 connecting the first and second spar caps 30a, 30b.

[0055] Whilst the connecting element 36 may be part of the second blade module 12b in some examples as shown in FIG. 1, in other examples, the modular wind turbine blade 10 may comprise one or more connecting elements 36 that are separate from both the first and second blade modules 12a, 12b.

[0056] For example, FIG. 2 shows a schematic exploded view of an example of a modular wind turbine blade 10 wherein the connecting element 36 is a separate part that is connected to both the first and second blade modules 12a, 12b. It will be appreciated that equivalent features previously described with reference to FIG. 1 will not be repeated here for conciseness.

[0057] Referring to FIG. 2, in examples wherein the connecting element 36 is a separate part, the connecting element 36 may comprise a second tapered end portion 38b in addition to the first tapered end portion 38a. The first and second tapered end portions 38a, 38b of the connecting element 36 are preferably configured for bonding to the respective tapered end portions 32a, 32b of the first and second spar caps 30a, 30b. As such, the first and second spar caps 30a, 30b may be connected via a double scarf joint, whereby the connecting element 36 forms a separate scarf joint 14 with each of the first and second spar caps 30a, 30b. The connecting element 36 may be referred to as a spar bridge in such examples.

[0058] In examples comprising a separate connecting element 36, the tapered end portion 32b of the second spar cap 30b may not extend from the second blade module 12b. Instead, the tapered end portion 32b of the second spar cap 30b may define a tapered recess 42b in the second blade module 12b. The second tapered end portion 38b of the connecting element 36 is preferably configured to fit within the tapered recess 42b of the second blade module 12b in such an example.

[0059] FIG. 3 shows a schematic cross-sectional view of an example of a joint 14 between the first tapered end portion 38a of the connecting element 36 and the tapered end portion 32a of the first spar cap 30a. The connecting element 36 and the first spar cap 30a are spaced apart in the spanwise direction (S) in FIG. 3 for clarity. However, it will be understood that the tapered end portions 32a, 38a of the first spar cap 30a and the connecting element 36 are configured for connection to one another. In an assembled modular wind turbine blade 10, it will be understood that the first tapered end portion 38a of the connecting element 36 and the tapered end portion 32a of the first spar cap 30a may be bonded together by adhesive (not shown).

[0060] The outer shells 20a, 20b of the first and second blade modules 12a, 12b are not shown in FIG. 3. It should be understood that FIG. 3 merely represents a schematic cross-sectional view of a joint 14 between the connecting element 36 and the first spar cap 30a. As such, it will be appreciated that the connecting element 36 may comprise a tapered end portion 32b of the second spar cap 30b extending from the second blade module 12b, as shown in FIG. 1 for example. Alternatively, the connecting element 36 may be separate from the first and second blade modules 12a, 12b, as shown in FIG. 2 for example. The following description of the connecting element 36 and the tapered end portion 32a of the first spar cap 30a is therefore applicable to both previously-described examples of FIGS. 1 and 2.

[0061] Referring to FIG. 3, the first spar cap 30a has an inner surface 44a and an outer surface 46a. The thickness T.sub.S of the spar cap 30a is defined between the inner surface 44a and the outer surface 46a. The first spar cap 30a comprises an intermediate thickness band 48a, and an inner thickness band 50a between the intermediate thickness band 48a and the inner surface 44a. The first spar cap 30a also comprises an outer thickness band 52a between the intermediate thickness band 48a and the outer surface 46a. The thickness bands 48a, 50a, and 52a each have a respective tapered end 54a, 56a, 58a within the tapered end portion 32a of the first spar cap 30a.

[0062] The tapered end 56a of the inner thickness band 50a and/or the tapered end 58a of the outer thickness band 52a of the first spar cap 30a has a lower rate of taper than the tapered end 54a of the intermediate thickness band 48a of the first spar cap 30a. That is to say the tapered end 54a of the intermediate thickness band 48a has a steeper taper than the tapered end 56a of the inner thickness band 50a and/or the tapered end 58a of the outer thickness band 52a. As shown in FIG. 3, in some examples the tapered ends 56a, 58a of both the inner and outer thickness bands 50a, 52a may have a lower rate of taper than the tapered end 54a of the intermediate thickness band 48a.

[0063] Referring now to the connecting element 36 which has an inner surface 44b and an outer surface 46b, the thickness T.sub.C of the connecting element 36 is defined between the inner and outer surfaces 44b, 46b. The connecting element 36 comprises an intermediate thickness band 48b, and an inner thickness band 50b between the intermediate thickness band 48b and the inner surface 44b. The connecting element 36 also comprises an outer thickness band 52b between the intermediate thickness band 48b and the outer surface 46b. The thickness bands 48b, 50b, and 52b each have a respective tapered end 54b, 56b, 58b within the first tapered end portion 38a of the connecting element 36.

[0064] Further, still with reference to the connecting element 36, the tapered end 56b of the inner thickness band 50b and/or the tapered end 58b of the outer thickness band 52b has a lower rate of taper than the tapered end 54b of the intermediate thickness band 48b of the connecting element 36. Accordingly, the tapered end 54b of the intermediate thickness band 48b therefore has a steeper taper than the tapered end 56b of the inner thickness band 50b and/or the tapered end 58b of the outer thickness band 52b. In some examples, the tapered ends 56b, 58b of both the inner and outer thickness bands 50b, 52b may have a lower rate of taper than the tapered end 54b of the intermediate thickness band 48b, as shown in FIG. 3.

[0065] Configuring the first spar cap 30a and connecting element 36 as described above, i.e. with different rates of taper for the respective inner thickness band tapered ends 56a, 56b and/or outer thickness band tapered ends 58a, 58b compared to the tapered ends 54a, 54b of the intermediate thickness bands 48a, 48b provides a number of advantages. In particular, such a configuration takes advantage of the non-uniform distribution of loads through the thickness T.sub.S, T.sub.C of the spar cap 30a and connecting element 36 to provide an advantageous compromise between strength and length of the joint 14.

[0066] In use, the inner thickness bands 50a, 50b and outer thickness bands 52a, 52b of the spar cap 30a and connecting element 36 typically take up and transfer higher loads than the intermediate thickness bands 48a, 48b. It is therefore advantageous to provide inner thickness bands 50a, 50b and/or outer thickness bands 52a, 52b having tapered ends 56a, 56b and 58a, 58b with a relatively shallow taper in order to transfer loads between the spar cap 30a and connecting element 36 more gradually, i.e. over a greater spanwise distance. Conversely, because the loads transferred between the respective intermediate thickness bands 48a, 48b are not as high as the loads transferred between the respective inner thickness bands 50a, 50b and outer thickness bands 52a, 52b in use, the intermediate thickness bands 48a, 48b may be configured with tapered ends 54a, 54b having a steeper taper.

[0067] This configuration advantageously facilitates the provision of a modular blade joint 14 that extends over a shorter spanwise length, without adversely affecting the strength and load transfer capabilities of the joint 14. In examples such as the modular blade 10 shown in FIG. 1, such a configuration may therefore reduce the spanwise extension of the connecting element 36 from the second blade module 12b, facilitating easier and safer transport of the blade module 12b (i.e. lower risk of damage) and easier assembly of the blade 10. In an example such as the modular blade 10 shown in FIG. 2, the above-described configuration may enable the use of a shorter separate connecting element 36, improving handling of the connecting element 36 and on-site assembly of the blade 10.

[0068] With reference still to FIG. 3, and more particularly to the example of the spar cap 30a, the inner and/or outer thickness band 50a, 52a of the spar cap 30a may each have a thickness t.sub.S1, t.sub.S2 of between 5% to 25% of the total thickness T.sub.S of the spar cap 30a. The intermediate thickness band 48a of the spar cap 30a preferably has a thickness t.sub.S3 of between 50% to 90% of the total thickness T.sub.S of the spar cap 30a.

[0069] As shown in FIG. 3, the spar cap 30a may comprise a stack of layers 60. For example, the layers 60 in the spar cap 30a may be pultrusions, i.e. strips formed in a pultrusion process. In preferred examples, the layers 60 may be made of carbon-fibre reinforced polymer. The layers 60 may be bonded together with resin (not shown) to form the spar cap 30a.

[0070] The intermediate thickness band 48a of the first spar cap 30a preferably comprises more layers 60 than the inner thickness band 50a of the first spar cap 30a. In some examples the intermediate thickness band 48a preferably comprises more layers 60 than the outer thickness band 52a of the first spar cap 30a. As shown in FIG. 3, in some examples it may be particularly advantageous to provide a spar cap 30a having an inner thickness band 50a and/or outer thickness band 52a that comprises only a single layer 60, with the intermediate thickness band 48a of the first spar cap 30a comprising a plurality of layers 60. Such an example may provide a significant reduction in overall length of the joint 14.

[0071] In preferred examples, the layers 60 in the spar cap 30a may be the same thickness. Because the intermediate thickness band 48a has a steeper taper, providing a spar cap 30a having more layers 60 in the intermediate thickness band 48a than the inner and/or outer thickness bands 50a, 52a advantageously reduces the spanwise length of the blade joint 14. Further, to form the shallower tapered ends 56a, 58a of the inner and/or outer thickness bands 50a, 52a, in some examples the or each layer 60 of the inner and/or outer thickness band 50a, 52a may taper over a longer spanwise length than each layer 60 of the intermediate thickness band 48a.

[0072] With reference now to the connecting element 36 shown by way of example in FIG. 3, the inner and/or outer thickness bands 50b, 52b of the connecting element 36 may each have a thickness t.sub.C1, t.sub.C2 of between 5% to 25% of the total thickness T.sub.C of the connecting element 36. Further, the intermediate thickness band 48b of the connecting element 36 may have a thickness t.sub.C3 of between 50% to 90% of the total thickness T.sub.C of the connecting element 36.

[0073] The connecting element 36 may comprise a stack of layers 62 in preferred examples. The layers 62 may be pultrusions that are preferably made of carbon-fibre reinforced polymer. In some examples, the intermediate thickness band 48b of the connecting element 36 may comprise more layers 62 than the inner and/or outer thickness band 50b, 52b of the connecting element 36. For example, the inner and/or outer thickness band 50b, 52b of the connecting element 36 may comprise a single layer 62 as shown in FIG. 3, and the intermediate portion 48b may comprise a plurality of layers 62. In preferred examples, the layers 62 in the connecting element 36 may be the same thickness. Each layer 62 of the inner and/or outer thickness band 50b, 52b of the connecting element 36 preferably tapers over a longer spanwise length than each layer 62 of the intermediate thickness band 48b. As such, the tapered layers 62 of the inner and/or outer thickness bands 50b, 52b form tapered ends 56b, 58b of the inner and/or outer thickness bands 50b, 52b with a shallower taper than the tapered end 54b of the intermediate thickness band 48b.

[0074] Referring to both the spar cap 30a and the connecting element 36 shown by way of example in FIG. 3, in some examples the tapered end 56a, 56b of the inner thickness band 50a, 50b of the spar cap 30a and/or connecting element 36 may define a curved taper. In some examples, the outer thickness band 52a, 52b of the spar cap 30a and/or connecting element 36 may also define a curved taper, as shown in FIG. 3.

[0075] In some examples, as shown in FIG. 3, the tapered end 54a of the intermediate thickness band 48a of the first spar cap 30a may define a linear taper. For example, in the tapered end portion 32a of the spar cap 30a, the thickness of the spar cap 30a may taper at a substantially uniform rate in the intermediate thickness band 48a. Referring still to FIG. 3, the tapered end 54b of the intermediate thickness band 48b of the connecting element 36 may also define a linear taper.

[0076] With reference now additionally to FIGS. 4a to 4d, these figures show a schematic representation of a plurality of different thickness progressions for a tapered end portion 32/38. The tapered end portion 32/38 in FIGS. 4a to 4d may be a tapered end portion 32 of a spar cap 30 or a tapered end portion 38 of the connecting element 36. As such, references to a thickness band 48, 50, 52, or a tapered end 54, 56, 58 apply equally to the corresponding features of the spar cap 30 and connecting element 36.

[0077] Referring to FIG. 4a, the tapered ends 54, 56, 58 of the intermediate, inner, and outer thickness bands 48, 50, 52 of the spar cap 30 or connecting element 36 may together define a generally S-shaped profile, as shown also in the example of FIG. 3. A generally S-shaped profile is particularly recognisable in examples wherein the inner and outer thickness bands 50, 52 of the spar cap 30 and/or connecting element 36 define a curved taper.

[0078] Alternatively, and as shown in FIG. 4b, the tapered ends 54, 56, 58 of the intermediate, inner, and outer thickness bands 48, 50, 52 of the spar cap 30 or connecting element 36 may together define a generally Z-shaped profile in the tapered end portion 32a, 38a of the spar cap 30a and/or connecting element 36. A generally Z-shaped profile is particularly recognisable in examples wherein the inner and outer thickness bands 50, 52 of the spar cap 30 and/or connecting element 36 define a substantially linear taper that has a lower rate of taper than the linear taper of the intermediate thickness band 48.

[0079] In some examples, as shown in FIG. 4c, the inner and/or outer thickness bands 50, 52 may comprise a plurality of rates of taper. For example, the inner and/or outer thickness band 50, 52 may taper linearly at a first taper rate over a first portion of a respective thickness band, and may taper further at a second taper rate over a second portion of the thickness band. The average rate of taper over the respective inner or outer thickness band 50, 52 is still lower than the rate of taper of the intermediate thickness band 48. Preferably each of the rates of taper in an inner or outer thickness band 50, 52 may be lower than the rate of taper of the intermediate thickness band 48.

[0080] Referring to FIG. 4d, in some examples the spar cap 30 and/or connecting element 36 may comprise one or more additional thickness bands 64. For example, the spar cap 30 and/or connecting element 36 may comprise one or more thickness bands 64 having a non-tapered end. In some examples, such a non-tapered thickness band 64 may be located between the intermediate thickness band 48 and the inner or outer thickness bands 50, 52. In some examples, such non-tapered thickness bands 64 may be located between the inner surface 44 and the inner thickness band 48, and/or between the outer surface 46 and the outer thickness band 52.

[0081] It will be appreciated that the orientation of the tapered end portion 32/38 shown in FIGS. 4a to 4d may be different for a tapered end portion 32 of a spar cap 30 and a tapered end portion 38 of a connecting element 36. For example, whilst the line 44 in FIGS. 4a to 4d may represent the inner surface 44 of a spar cap 30, it will be appreciated that line indicated by 44 may equally represent an outer surface 46 of a spar cap 30, an inner surface 44 of a connecting element 36, or an outer surface 46 of a connecting element 36, in other examples. As such it will be appreciated that the thickness progressions shown schematically in FIGS. 4a to 4d are non-dimensional and are applicable to both spar caps 30 and connecting elements 36.

[0082] Finally, referring briefly to FIG. 5, which again shows the joint 14, in some examples the blade 10 may comprise an inner patch 66 applied over an interface 68 between the inner thickness band 50a of the first spar cap 30a and the inner thickness band 50b of the connecting element 36. In some examples, the modular wind turbine blade 10 may comprise an outer patch 70 applied over an interface 72 between the outer thickness band 52a of the first spar cap 30a and the outer thickness band 52b of the connecting element 36. The patch 66, 70 may comprise a stack of plies 74 of fibrous material, and may be configured to transfer a proportion of the loads across the joint 14 between the spar cap 30a and the connecting element 36. A patch 66, 70 may additionally help to resist peel loads that act to peel apart the tapered ends 56a, 56b and 58a, 58b of the inner and outer thickness bands 50a, 50b and 52a, 52b when the modular blade 10 is in use.

[0083] It will be appreciated that the above description and accompanying figures are provided merely as an example of the present invention. Many alternatives to the specific examples described above are therefore possible without departing from the scope of the invention as defined in the appended claims.

[0084] For example, whilst the tapered end portions 32, 38 of the spar cap 30 and connecting element 36 are configured with a complementary shape in the accompanying figures, in some examples, it will be appreciated that configuring the modular wind turbine blade with one or more of the tapered ends 56a, 56b and 58a, 58b of the inner and outer thickness bands 50a, 50b and 52a, 52b of the spar cap 30 and connecting element 36 having a lower rate of taper than the tapered end 54a, 54b of the respective intermediate thickness band 48a, 48b may provide an appreciable reduction in the length of the joint 14 without unduly compromising joint strength.

[0085] For example, whilst not shown in FIG. 3 or 5, in some examples the tapered end 56a of the inner thickness band 50a of the spar cap 30 may have a lower rate of taper than the intermediate thickness band tapered end 54a of the spar cap 30, but the tapered end 56b of the inner thickness band 50b of the connecting element 36 may not necessarily have a lower rate of taper than the intermediate thickness band tapered end 54b of the connecting element 36. In such an example the tapered ends 58a, 58b of the outer thickness bands 52a, 52b of the spar cap and connecting element 30, 36 may similarly not necessarily have a lower rate of taper than the tapered ends 54a, 54b of the respective intermediate thickness bands 48a, 48b. That is to say, the tapered end portion 38a of the connecting element 36 may have a relatively steep taper throughout, the tapered ends 54a, 58a of the intermediate and outer thickness bands 48a, 52a of the spar cap 30 may similarly have a relatively steep taper, and the tapered end 56a of the inner thickness band 50a of the spar cap 30 may have a relatively shallow taper.

[0086] In preferred examples, each of the spar cap 30 and connecting element 36 preferably has at least one thickness band 50a, 50b, 52a, 52b having a tapered end 56a, 56b, 58a, 58b with a lower rate of taper than the tapered end 54a, 54b of the respective intermediate thickness band 48a, 48b of the spar cap 30 or connecting element 36. More preferably, at least one of the inner or outer thickness bands 50a, 52a of the spar cap 30 has a tapered end 56a, 58a with a lower rate of taper than the intermediate thickness band tapered end 54a, and additionally at least the other of the inner or outer thickness bands 50b, 52b of the connecting element 36 has a tapered end 56b, 58b with a lower rate of taper than the intermediate thickness band tapered end 54b. As such, the modular wind turbine blade preferably comprises at least one inner thickness band 50 having a tapered end 56 with a lower rate of taper than the tapered end 54 of an intermediate thickness portion 48, and at least one outer thickness band 52 having a lower rate of taper than the tapered end 54 of an intermediate thickness band 48.

[0087] However, in more preferred examples, the tapered end portion 32 of the spar cap 30 and the tapered end portion 38 of the connecting element 36 have a complementary shape, as shown in FIGS. 3 and 5 for example. That is to say, the tapered ends 56 of the inner thickness bands 50 of both the spar cap 30 and the connecting element 36 preferably have a lower rate of taper than the tapered ends 54 of the respective intermediate thickness bands 48 of the spar cap and connecting element 30, 36. Additionally or alternatively, the tapered ends 58 of the outer thickness bands 52 of both the spar cap 30 and the connecting element 36 preferably have a lower rate of taper than the tapered ends 54 of the respective intermediate thickness bands 48 of the spar cap 30 and connecting element 36. In the most preferred examples, the inner thickness bands 50 of the spar cap 30 and connecting element 36 have complementary tapered ends 56, and the outer thickness bands 52 of the spar cap 30 and connecting element 36 also have complementary tapered ends 58.

[0088] Further, in the example shown in FIG. 1, the tapered end portion 32a of the first spar cap 30a defines a tapered recess 42a in the first blade module 12a, and the tapered end portion 32b of the second spar cap 30b extends from the second blade module 12b. However, in some other examples, the modular wind turbine blade 10 may comprise first and second spar caps 30a, 30b that both extend from their respective blade modules 12a, 12b. That is to say, the modular blade 10 may comprise a first blade module 12a having a first spar cap 30a with a tapered end portion 32a that extends from the first blade module 12a, and a second blade module 12b with a second spar cap 30b having a tapered end portion 32b that also extends from the second blade module 12b. The tapered end portions 32a, 32b of the first and second spar caps 30a, 30b in such an example are preferably mutually opposed and connected by a connecting element 36, such as a spar bridge, that forms scarf joints 14 with both the first and second spar caps 30a, 30b as previously described. In such an example, a fairing (not shown) may be provided around the part of the blade 10 comprising the joints 14 and the connecting element 36.

[0089] It will be appreciated that the first and second blade modules 12a, 12b may each comprise a plurality of spar caps 30. However, for conciseness only a first spar cap 30a of the first blade module 12a, and a second spar cap 30b of the second blade module 12b, are described herein. It will be appreciated that the description provided in relation to the first and second spar caps 30a, 30b is equally applicable to any other pair of spar caps 30 that are connected when assembling the modular wind turbine blade 10.

[0090] Further, whilst the description above has been provided primarily in relation to the joint 14 between the first spar cap 30a and the connecting element 36, it will be appreciated that any description of the joint 14, and features of the spar cap 30a and connecting element 36, is equally applicable to a joint 14 between the second spar cap 30b and the connecting element 36 for examples wherein the first and second spar caps 30a, 30b are connected via a separate connecting element 36.

[0091] It will be appreciated that the description provided above serves to demonstrate a plurality of possible examples of the present invention. Features described in relation to any of the examples above may be readily combined with any other features described with reference to different examples without departing from the scope of the invention as defined in the appended claims.