Wind Generator Innovative Blade Design: Variable Twist and Start-Up Control

This paper presents the preliminary results obtained in the VENTURAS (VENTo: Una Risorsa Altamente Sfruttabile or 'wind: a highly exploitable resource') project, funded by the Italian Environmental, Land and Sea Protection Ministry, within a call for the funding of research projects aimed at improving the energy efficiency measures and the use of renewable energy sources in urban areas. This project addresses to improve the efficiency and to widen the range of the wind speed at which the micro wind turbines operate effectively and safely. This goal is achieved by developing variable pitch blades, which have morphing capabilities that enables the control system to select the optimum twist law along the blade, to optimize the efficiency also in non-nominal conditions. The proposed control strategy aims at maximizing the rotor efficiency, by maintaining the rotor in the nominal working condition. The control algorithm is based on a finite state machine, which commands the twist law to the blades, according to different strategies, predesigned for each working condition. At low wind speed, the control system changes the blade twist law, in order to maintain the angular speed and maximize the electrical efficiency. In this paper, the performance of different start-up strategies are compared.