Systems and methods for pitching of rotor blades
A wind turbine includes a hub rotatable about an axis and a blade coupled to the hub. The blade includes an inner blade portion having a first end and a second end. The inner blade portion is coupled to the hub at the first end and extends radially outward from the hub to the second end. The blade further includes an outer blade portion having a first end and a second end. The first end of the outer blade portion is pivotably coupled to the second end of the inner blade portion.
1. A wind turbine comprising:
a hub rotatable about a hub axis;
a blade coupled to said hub and defining a longitudinal axis, said blade comprising:
an inner blade portion comprising a first end and a second end, said inner blade portion coupled to said hub at said first end and extending radially outward from said hub to said second end; and
an outer blade portion comprising a first end and a second end, said first end of said outer blade portion pivotably coupled to said second end of said inner blade portion; and
a cable coupled to said inner blade portion at a first end of said cable and coupled to said outer blade portion at a second end of said cable, said cable extending within said inner blade portion and tensioned to provide an axial load on said outer blade portion.
2. The wind turbine in accordance with claim 1 , wherein the longitudinal axis extends from said first end of said inner blade portion to said second end of said outer blade portion, and wherein said outer blade portion is configured to rotate about the longitudinal axis relative to said inner blade portion.
3. The wind turbine in accordance with claim 1 , wherein the longitudinal axis extends from said first end of said inner blade portion to said second end of said outer blade portion, and wherein said first end of said inner blade portion is pivotably coupled to said hub such that said inner blade portion is configured to rotate about the longitudinal axis.
4. The wind turbine in accordance with claim 1 , wherein said outer blade portion extends obliquely relative to said inner blade portion.
5. The wind turbine in accordance with claim 1 further comprising a rotatable element extending between said inner blade portion and said outer blade portion, said rotatable element comprising a first end coupled to said inner blade portion and a second end coupled to said outer blade portion.
6. The wind turbine in accordance with claim 5 , wherein said rotatable element second end is rotatable relative to said rotatable element first end to facilitate rotating said outer blade portion relative to said inner blade portion.
7. The wind turbine in accordance with claim 5 , wherein said rotatable element is an elastic flexure bearing.
8. The wind turbine in accordance with claim 7 , wherein said second end of said rotatable element is rotatable at least +/− one degree relative to said first end of said rotatable element.
9. The wind turbine in accordance with claim 5 further comprising a support structure positioned within said inner blade portion, said rotatable element further comprising a body extending a length from said support structure to said outer blade portion, wherein said body is configured for elastic deformation about the length of said body.
10. The wind turbine in accordance with claim 1 , wherein said cable is a first cable, and wherein said wind turbine further comprises a second cable extending within said inner blade portion and coupled to said inner blade portion and said outer blade portion, said first cable and said second cable each extending between said inner blade portion and said outer blade portion.
11. The wind turbine in accordance with claim 1 , wherein said first end of said cable is coupled at said first end of said inner blade portion.
12. The wind turbine in accordance with claim 11 , wherein said cable extends within said outer blade portion.
13. The wind turbine in accordance with claim 1 further comprising a rotatable element extending between said inner blade portion and said outer blade portion, said rotatable element comprising a first cup positioned at least partially within said inner blade portion, a second cup positioned at least partially within said outer blade portion, and a roller element extending between said first cup and said second cup.
14. The wind turbine in accordance with claim 13 , wherein said second end of said cable is attached to said second cup.
15. The wind turbine in accordance with claim 13 , wherein said rotatable element is a tapered roller bearing.
16. A blade for use in a wind turbine system comprising:
an inner blade portion comprising a first end and a second end;
an outer blade portion comprising a first end and a second end, said first end of said outer blade portion coupled to said second end of said inner blade portion;
a rotatable element extending between said inner blade portion and said outer blade portion, said rotatable element comprising a first end coupled to said inner blade portion and a second end coupled to said outer blade portion, wherein said rotatable element second end is rotatable relative to said rotatable element first end to facilitate rotating said outer blade portion relative to said inner blade portion; and
a cable coupled to said inner blade portion at a first end of said cable and coupled to said outer blade portion at a second end of said cable, said cable extending within said inner blade portion and tensioned to provide an axial load on said outer blade portion.
17. The blade in accordance with claim 16 , wherein said rotatable element is an elastic flexure bearing.
18. The blade in accordance with claim 17 , wherein said second end of said rotatable element is rotatable at least +/− one degree relative to said first end of said rotatable element.
19. The blade in accordance with claim 16 further comprising a support structure positioned within said inner blade portion, said rotatable element further comprising a flexible support member extending from said support structure to said outer blade portion.