The wind power harvested by a wind turbine increases with wind speed and rotor diameter. A greater rotor diameter requires a greater nacelle height which entails the further advantage that wind speed typically increases with height above ground. Thus, with the desire for always greater rated wind turbine powers, there is a trend to higher wind turbine towers. As wind speeds and rotor diameters increase, so do the lateral loads on the tower. For this reason the average diameters of wind turbine towers have been increasing throughout the years.
Usually, wind turbine towers are fabricated from steel or concrete. The towers are produced in cylindrically or frustoconical sections which then are brought to the site where the wind turbine is to be erected. The dimensions of such sections of tall wind turbine towers are approaching limits set by the infrastructure of various countries. Such limiting aspects may include headroom under bridges, tunnel heights, maximum allowable weight or the radii of roundabouts.
The increasing number of wind power installations is also causing difficulties because the equipment needed for the transportation of the tower sections is not available in the required quantities. Thus, installation of new wind turbines may be delayed due to logistic problems. For this reason WO 01/07731 proposes constructing the wind turbine tower at the installation site of the wind turbine by using a slipforming technique.