Innovative blade design for wind generator application

This paper is focused on 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. The scope of the project is to develop an innovative propeller concept to improve the efficiency and the working capabilities of micro wind turbines, widening the range of the wind speed for which the turbine can transform energy effectively and safely. This new propeller concept is based on a variable pitch blade, which has 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 final layout identified for the proposed wind turbine will be presented; the pylon contains the power supply and an On Board Computer (OBC) for the active control loop, whereas, the nacelle hosts the motors for yaw control and pitch/twist control. The general idea of the morphing control system is to obtain a twist law theta( r ) so as to allow the optimal rotor operation for different working conditions. The proposed control strategy aims at maximizing the rotor efficiency, calculated as the product of the mechanical and the electrical efficiencies by maintaining the rotor in the nominal working condition. At low wind speeds, the control system changes the blade twist law, in order to maintain the angular speed at a certain level so that the electrical efficiency is always maximized.