Design of passive, stall controlled wind turbine blade

BackgroundThere in an increased interest for offshore wind farms due to their promising capability for large scale energy production. However offshore wind turbines need to be designed such that they require minimum amount of maintenance due to the fact that the maintenance cost of offshore wind turbines is significantly larger than their onshore counterparts. One way of achieving this is looking at the control systems, especially the pitch system and finding a way of replacing it or at the very least minimizing its operation. In addition, the removal of the pitch system has snow ball effect on the total mass of the wind turbine thus reducing further the initial capital cost. An alternative approach to regulate the power is the stall control method. The research goal is to design stall controlled wing turbine using the twist coupling effect of the structure to induce stall while minimizing the cost of energy.For the stall control method, the wind turbine blade is rotated(active or passive) to stall thus reducing the torque and power. In order to regulate the power production of wind turbine passively, the structural twist coupling is optimized using ISO geometric design approach.

Definition of B-splines(Bi):

= non-uniform knot vector in

Properties of B-splines:• Piecewise polynomials of degree p• Non-negative partition of unity• The function is non zero in Progress• Cross-sectional modeller

• Parametric model of wind turbine blade• Beam model

• Shell model

• NURB based non-linear Timoshenko beam

Publications

- E. Zupan, M. Saje, D. Zupan, (2009) “The quaternion-based three dimensional beam theory”, Computational methods, pp 3944-3956

- M.M. Willaert, M.M. Abdalla, Z. Gurdal, (2010) “A simple finite element cross-sectional modelling of thin-walled beams”

- J. Cottrell, T. Huges, Y. Bazilevs, (2009) “Finite Element Procedures”, Wiley

- J. Cottrell, T. Huges, Y. Bazilevs, (2009) “Isogeometric Analysis”, Wiley

2 bladed, 5MW stall controlled wind turbine

Method for twist coupling

• Geometrical

• Structural

• Material

Iso-Geometric Analysis(IGA):Concept

Difference between CAD-FEM and IGA

• CAD and IGD use the same basis functions• No approximation of the geometry during

analysis• Circumvent difficulty during mesh generation• PDEs are solved using NURBS

Parameterization of wind turbine blade

• Beam axis:

• Airfoil:

• Twist:

• Cg:

•

PhD Candidate: Etana FeredeDepartment: AWEPSection: Wind Energy & StructuresSupervisor: dr. M. M. AbdallaPromoter: dr. G.J.W. van BusselStart date: 1-10-2011Funding: FLOWCooperation: 2-B Energy

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