Special Issues on Design Optimization of Wind Turbine Structures

A wind turbine is a device that exploits the wind’s kinetic energy by converting it into useful mechanical energy. It basically consists of rotating aerodynamical surfaces (blades) mounted on a hub/shaft assembly, which transmits the produced mechanical power to the selected energy utilizer (e.g. milling or grinding machine, pump, or generator). A control system is usually provided for adjusting blade angles and rotor position to face the wind properly. All units are supported by a stiff tower structure, which elevates the rotor above the earth’s boundary layer. There are two common types: horizontal-axis and vertical-axis wind turbines. In the former, which dominate today’s markets, the blades spin about an axis perpendicular to the tower at its top (see Fig.1), while in the latter they spin about the tower axis itself. In fact, wind turbines have been used for thousands of years to propel boats and ships and to provide rotary power to reduce the physical burdens of man. From the earliest