Chapter 6 - Nacelles and Towers

Abstract

The nacelle of a wind turbine houses the drive train and other tower-top components. It sits on top of a yaw bearing that allows it to rotate as the wind direction changes. The nacelle must be accessible for maintenance and repair work. Access is usually via a lift and ladders within the tower. The nacelle is usually assembled at the factory and must be lifted to the top of the tower using specialist lifting equipment. Most modern wind turbines also include real-time condition monitoring systems which are also housed in the nacelle. The tower upon which the nacelle is mounted is usually two to three times the rotor blade length although it may be taller to allow the blades to access higher wind speeds. Most large wind turbine towers are constructed from tubular steel sections although some may use a tubular concrete base. For smaller wind turbines, lattice steel structures are still common as are poles stabilized with guys. As sizes increase, so new techniques such as space frame and bolted sectional construction are being explored. Onshore turbine foundations are usually gravity, or spreading foot foundations.