Combining the best features of stall and pitch control is also the aim of a project supported under the EU Joule research and development programme (Windpower Monthly, January 1998). But it tackles the issue in a completely different way -- through blade design using a device built into the blade tip. Project leader Stork Product Engineering of the Netherlands has shown the feasibility and the mechanical durability of the proposed tip mechanism in a previous project. The TenTorTube is a long slender tube made of composite material. Loadings on the wind turbine blade deform the material so that the blade twists, changing the angle of attack. The new Joule project aims to take the work forward to a stage where a commercial design -- possibly undertaken by one of the partners in the project, Dutch rotor blade manufacturer Aerpac -- can be manufactured. Complex aeroelastic modelling is needed to simulate the performance of the blade and early work has concentrated on developing appropriate prediction techniques. The material for the tube will be aramid fibre reinforced epoxy as the earlier trial showed this to be promising.
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