Generally, efficiency increases along with turbine blade lengths. The blades must be stiff, strong, durable, light and resistant to fatigue. Materials with these properties include composites such as polyester and epoxy, while glass fiber and carbon fiber have been used for the reinforcing. Construction may involve manual layup or injection molding. Retrofitting existing turbines with larger blades reduces the task and risks o. Wind turbine design is the process of defining the form and configuration of a to extract energy from the. An installation consists of the systems needed to capture the wind's energy, point the turbine into the wind, convert into, and other systems to start, stop, and control the turbine. In 1919, German physicist showed that for a hypothetical ideal wind-energ.