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Content archived on 2024-05-07

Soft rotor design for flexible turbines

CORDIS provides links to public deliverables and publications of HORIZON projects.

Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .

Exploitable results

The project has consisted in development and testing of a two-bladed soft rotor for an existing 15 kW flexible wind turbine. The new concept is characterized as a free yawing down wind turbine with nacelle tilting flexibility and a two-bladed teetering rotor with three-point supported blades with build-in structural couplings. The power and the loads are controlled by active stall and active coning. The project has constituted a design process, however with the main emphasis on determination of optimal characteristics for the turbine, perceived as a universal concept. The concept has been developed by extensive application of aeroelastic predictions, numerical optimisation and stability analysis in order to obtain optimal aeroelastic response and minimal loads. The calculations and succeeding model tests have been performed particularly for a 13 m diameter rotor, but all conceptual design principles have been focused on application to large MW turbines. The intention with this has been to make the results generally applicable and not limited to the development of the specific wind turbine. The flexible blades and the principle of active coning allows the blades to deflect with the wind to such an extent that the loads are much reduced during stand still in extreme winds. Comparisons of predictions for this concept and a similar rigid rotor show that the blade and rotor loads are reduced to between 25 and 50 % during operation as well as during stand still in extreme winds. This, however, is not a universal ratio for the relation between the loads on the two concepts. In particular this relation depends upon the size of the turbine. The aeroelastic predictions have covered normal operation, stand still in extreme winds and abnormal upwind operation. Corresponding conditions have been investigated with the prototype turbine, and the measurements have to a large extent verified the predicted turbine characteristics. The turbine has been operating perfectly in all conditions, and it has as a result of the experiments and measurements not been necessary to correct one single parameter setting, in order to obtain the estimated optimal characteristics - not even the blade pitch setting. The work has confirmed that substantial load reductions can be obtained for this concept in comparison to the traditional ones, and that the applied calculation tools are applicable even for such an extreme configuration. Altogether the experience from conducting the project is that the resulting design represents a frame for a quite universal concept that contains great potentials for future detailed developments and refinements.

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