An innovative variable shroud for micro wind turbines.

In this work, a 370-W small wind turbine was developed which is equipped to a controllable nuzzle-diffuser duct. The developed duct is consisting of a fixed ring and a two-piece diffuser which can rotate on each other and so the diffuser wall opening will have altered from 0 to 180°. This mechanism is developed to control speed-up ratio and drag forces acting on the turbine structure in high ranges of wind speeds. The rotor is designed using BEM algorithm and the duct geometry is reached by CFD works considering the atheistic aspect of view. As the turbine is designed for a comprehensive research project, so it contains several a subsystems like an electromagnetic brake, external electric starter motor, electromagnetic flywheel, variable nacelle, etc. The designed mechanism fabricated using several machining processes as turning, milling, boring, drilling, welding and rolling works. The turbine performance implemented in a low-speed wind tunnel. Experimental results show a comprehensive raise in power generation and rotor speed by shrouded wind turbines. In the 180-degree diffuser wall opening, the augmentation ratio in average is 39.75% while the ratio is 28.5% for a complete diffuser augmented wind turbine. The rotor speed-up ratio for them is 53 and 74% respectively. • The fully closed duct augments the turbine power by 37% compared with the bare one. • The fully closed duct raises the rotor speed by 61% comparing to the bare one. • The half-closed duct augments the turbine power by 37% comparing to the bare one. • The half-closed duct raises the rotor speed by 80% compared with the bare one. • The controlled duct augments the power and rotor speed by 50 and 61% respectively. [ABSTRACT FROM AUTHOR]