US Patent 8231347 Mass-centralizing blade extension drive mount locations for wind turbine

Drive units for variable-length rotor blades are located so as to move mass closer to the center of a wind turbine rotor. In some cases, drive units are located within a root portion of a base blade of a blade assembly. In other cases, drive units are located outside of the blade assemblies. In some such cases, drive units are contained within separate couplers used to connect blade assemblies to a wind turbine rotor hub. In other cases, one or more drive units are located within a rotor hub.