Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Typically, to initially install a rotor blade onto the hub and/or to remove one of the existing rotor blades from the hub, a significantly large crane must be transported to the wind turbine site in order to provide a means for raising and/or lowering the rotor blade relative to the hub. Unfortunately, it is often extremely expensive to both transport the crane to the wind turbine site and operate the crane for the amount of time necessary to install and/or remove the rotor blade(s). As a result, the costs of employing such large cranes currently accounts for a significant portion of the overall costs associated with initial wind turbine installations and rotor blade maintenance operations.
In addition, the rotor blades are typically attached to an inner race of a pitch bearing via a plurality of root bolts. The root bolts are commonly threaded into a barrel nut located in the blade root. The barrel nut is essentially a short round bar that has a threaded hole perpendicular to the longitudinal axis of the barrel nut at a substantially center location thereof. Thus, certain methods for lifting and/or lowering a wind turbine rotor blade may include replacing a plurality of the barrel nuts in the blade root of the rotor blade with lifting hardware that allows the rotor blade to be lifted and/or lowered from inside of the hub without using a crane.
Certain rotor blades, however, do not utilize barrel nuts within the blade root. Thus, previously discussed lifting and/or lowering methods cannot be easily utilized. Accordingly, the art is continuously seeking systems and methods for manufacturing rotor blades that provide blades that can be easily removed and/or installed without the use of a significantly large crane.