WIND TURBINE BLADE

Abstract

Wind turbine blades with de-icing and/or anti-icing systems including at least one heating unit disposed along the blade's length and between the blade's chord, wherein each heating unit in turn comprises a plurality of heating elements connected both in series and in parallel in a matrix configuration by overlaps or cross-adjacent junctions between adjacent heating elements order to change the electric heating current flow disposing of any additional terminals cables and further enabling to generate a gradually increasing heat flux from the blade root towards the blade tip and from the trailing edge towards the leading edge through each individual heating unit adapting accurately to heat flux demand and hence reducing energy consumption for de-icing and/or anti-icing.

Claims

1. A wind turbine blade comprising; a blade root; a blade tip; a leading edge; a trailing edge; and at least one heating unit comprising two terminals, configured to be fed by an electric heating current and disposed between the blade root the blade tip and between the leading edge and the trailing edge; wherein the at least one heating unit comprises a plurality of heating elements arranged both in parallel and in series in a matrix configuration by at least one string overlap between adjacent heating elements connected in series and at least one cross-adjoining junction between the adjacent heating elements connected in parallel, allowing to change an electric heating current flow disposing of any additional terminals cables and further enabling to generate an accurately increasing heat flux from the blade root towards the blade tip and from the trailing edge towards the leading edge through the at least one heating unit.

2. The wind turbine blade according to claim 1, wherein the at least one string overlap comprises a length of 0.5-20 cm.

3. The wind turbine blade according to claim 2, wherein the at least one string overlap comprises a length of 1-3 cm.

4. The wind turbine blade according to claim 1, further comprising at least one additional conductive element overlapping two adjacent heating elements.

5. The wind turbine blade according to claim 1, wherein the at least one cross-adjoining junction is a cross overlap between adjacent heating elements and an overlap comprises a length of 0.5-3 cm.

6. The wind turbine blade according to claim 1, wherein the at least one cross-adjoining junction comprises a distance apart between adjacent cross heating elements, the distance apart comprising a length between 0 to 50 mm.

7. The wind turbine blade according to claim 1, wherein each heating element of the plurality of heating elements comprises parameters of: a width, a length, a thickness and a resistivity, and each of the plurality of heating elements comprising a variable combination of the parameters inside a heating unit.

8. The wind turbine blade according to claim 1, wherein the electric heating current is applied in a longitudinal direction.

9. The wind turbine blade according to claim 8, wherein the at least one heating unit has a higher resistance towards the blade tip.

10. The wind turbine blade according to claim 8, wherein the at least one heating unit has a lower resistance towards the blade leading edge.

11. The wind turbine blade according to claim 1, wherein the electric heating current is applied in a transversal direction.

12. The wind turbine blade according to claim 1, further comprising a plurality of heating units disposed in parallel along the blade.

13. The wind turbine blade according to claim to claim 12, wherein the at least one heating unit is fed individually with different voltages.

14. The wind turbine blade according to claim 1, wherein the plurality of heating elements are conductive fabric composite or paint.

Description

BRIEF DESCRIPTION

[0035] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0036] FIG. 1 illustrates a graph showing the thermal losses along the radius of a conventional wind turbine blade for a plurality of temperature increases;

[0037] FIG. 2a illustrates a schematic view of a first preferred configuration clearly showing a plurality of heating units disposed along the blade longitudinal direction;

[0038] FIG. 2b illustrates a schematic view of a second preferred configuration clearly showing one single heating unit disposed along the blade longitudinal direction;

[0039] FIG. 3 illustrates a first preferred embodiment of a heating unit clearly showing six heating elements connected in series and in parallel by string overlaps and cross-adjoining junctions respectively;

[0040] FIG. 4 illustrates a second preferred embodiment of a heating unit clearly showing six heating elements with variable width and material; and

[0041] FIG. 5 illustrates a third preferred embodiment of a heating unit clearly showing six heating elements wherein the width of two single elements is variable along its length.

DETAILED DESCRIPTION

[0042] FIG. 1 illustrates a graph showing the thermal losses along the radius of a conventional wind turbine blade for a plurality of temperature increases. Therefore, it can be seen how the heat flux demand and hence in turn the exact heat flux that should be generated ideally varies gradually as the radius of the blade increases.

[0043] Additionally, the heat flux demand increases gradually from the trailing edge until the leading edge (not shown) and further, it may be found that the surface to be heated covers the leading edge until a certain distance towards the trailing edge, and the distance may not be constant along the blade.

[0044] Thus, it is illustrated the significance importance of optimizing the heat flux generated along each single section of the radius of the blade and along its chord in each single section of the blade to reduce the energy consumption for de-icing and anti-icing.

[0045] FIG. 2a illustrates a schematic view of a first preferred configuration clearly showing a wind turbine blade comprising a blade root (1), a blade tip (2), a leading edge (3), a trailing edge (4).

[0046] FIG. 2a also illustrates that the wind turbine blade comprises a plurality of heating unit (5) comprising two terminals (6), adapted to be fed by an electric heating current by a conductor (C) and wherein each heating unit (5) is disposed along the longitudinal direction, between the blade root (1) and the blade tip (2) and between the leading edge (3) and the trailing edge (4),

[0047] Additionally, FIG. 2a illustrates that each heating unit (5) comprises a plurality of heating elements (7).

[0048] FIG. 2b illustrates a schematic view of a second preferred configuration clearly showing that the wind turbine blade comprises a single heating unit (5) extended until the blade tip (2).

[0049] FIG. 3 illustrates a detailed schematic view of a first preferred embodiment of a single heating unit (5) according to the first configuration described above. This is with a plurality of heating units (5) along the blade.

[0050] FIG. 3 clearly shows a single heating unit (5) comprising six heating elements (7) arranged both in parallel and in series in a matrix configuration by string overlaps (9) between adjacent heating elements (7) connected in series and by cross-adjoining junctions (8) between adjacent heating elements (7) connected in parallel.

[0051] The heating unit (5) described in FIG. 3, is able to change the electric heating current flow (I) without including extra terminal cables. This is a significant advantage as every terminal cable should be connected to a conductor located at inner surface of the blade, which causes great inconvenience for assembly the heating system to a wind turbine blade.

[0052] Additionally, by changing the resistance of each heating element (7) the heating unit (4) is further able to generate accurately an increasing heat flux from the blade root (1) towards the blade tip (2) and from the trailing edge (4) towards the leading edge (3) through each heating unit (5). That is, along the longitudinal direction of blade and along the chord.

[0053] In a first embodiment shown in FIG. 3, this is achieved by changing the material and/or the geometry of heating element (5) and therefore modifying its resistivity and as a consequence its resistance.

[0054] In a first embodiment heating elements E1 and E3 are made of the same material, likewise are E4 and E6, but of different materials between each group thereof. Heating elements E2 and E5 comprise each else another different material. Therefore, linear resistivity and hence resistance is changed and optimized according to desired heat flux at a precise radius and chord portion of the blade.

[0055] Additionally, the width of the elements is also varied, in particular the width of elements E2 and E5 is reduced in relation to the width of elements E1, E3, E4 and E6. Again, with the object of optimizing the required heat flux demand at each precise portion of the blade.

[0056] Note, that optimizing the resistance of every individual heating element (7) according to the specific configuration, the heating flux can be accurately optimized through every single heat unit (5) and as a consequence more accurately optimized along the longitudinal and cross-sectional direction of the blade.

[0057] FIG. 3 also shows that the cross-adjoining junction (8) between elements E1 and E4 with E2 is a cross overlap while the cross-adjoining junction (8) between elements E4 and E6 with E5 is an adjacent junction with no distance apart or overlap thereof.

[0058] FIG. 4 illustrates a detailed schematic view of a second preferred embodiment of a single heating unit (5) according to the first configuration previously described.

[0059] FIG. 4 clearly shows six heating elements (7) arranged both in parallel and in series in a matrix configuration by string overlaps (9) between adjacent heating elements (7) connected in series and by cross-adjoining junctions (8) between adjacent heating elements (7) connected in parallel.

[0060] In this second embodiment shown in FIG. 4, the width of the heating elements E4 and E6 linearly decreases along the length of the heating elements (7) thereof, thus increasing the resistance as the width shortens.

[0061] Furthermore, heating elements E1 and E3 are made of the same material, likewise to E4 and E6 but different materials or geometry between each other thereof. Heating elements E2 and E5 comprise each else another different material or geometry to the previously mentioned.

[0062] Additionally, in FIG. 4, it is shown that the cross-adjoining junction of E4 and E6 with E5 is of 0 mm. Nevertheless, note that even a separation of a distance apart of some millimeters could be feasible for cross-adjoining junctions (not illustrated).

[0063] FIG. 5 illustrates another preferred embodiment of a heating unit (5). It can be seen from FIG. 5, that the matrix configuration does not need to have an equal number of rows and columns.

[0064] FIG. 5 shows heating element E1 and E3 directly connected to the terminals (6) and wherein the width of the heating elements E1 and E3 is reduced linearly along its corresponding length. Furthermore, the heating elements E1 and E3 have the same material and resistivity and in turn are overlapped to elements E2, E4 and E5 which in turn each comprise else different material and length.

[0065] FIG. 5 also shows an additional conductive element (10) which overlap both heating elements E4 and E5. This may be accomplished by a metallic mesh or any other conductive sheet, fabric or mesh between two strings overlapped (8) heating elements (7). The use of a metallic mesh between two overlapped heating elements (7) can only be applied for those in transversal direction respect the electrical current flow, this is for string overlapped (9) t heating elements (7).

[0066] Note that in any of the embodiments described, the heat flux can be optimized along every single heat unit (5) and hence able to achieve an extremely accurate gradual heat flux along each individual portion of the blade to adapt to the heating flux ideally demanded. In other words, by modifying the amount of heating elements (5) in series and in parallel, thus the matrix configuration, and further modifying the material, the width and/or the thickness of every heating element (5), a very accurate profile of the heat flux to be generated along the blade can be achieved adapting very accurately to the ideal heat flux demand. Thus, the energy consumption for de-icing and anti-icing can be greatly reduced and consequently energy yield and production to the grid greatly increased. This is achieved without increasing the number of terminal cables (6) for each heating unit (5).

[0067] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0068] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.