WindPACT Rotor Design Study: Hybrid Tower Design; Period of Performance: 29 June 2000 -- 28 February 2004

The cost of a wind turbine tower can represent as much as 20% of the cost of an entire megawatt-scale horizontal axis wind turbine (HAWT) and as much as 10% of the total cost of energy. The tower is a major cost component, and its design is important: Its structural properties are key to the response of the rotor; its height determines the wind regime that the rotor experiences; it allows accessto the turbine nacelle and rotor; and it houses components of the electrical connection and the control and protection systems. Most large wind turbines installed in the United States use self-supporting steel tubular towers. The diameter of these tubes is limited by the size that can be transported by road (approximately 4.3 m). The base dimensions of a truss tower are not restrained by thislimit, but trusses may require more maintenance. Guyed tube towers have been used, but they represent additional foundation costs and inconvenience. Addressing these limitations may lead to an alternative that avoids the problems. For this reason, the WindPACT Rotor Design Study was modified to include a study of a hybrid tower to determine the technical and economic feasibility of such a design.