We have been using windmills as an alternate form of energy for a long time now. Scientists have experimented with many designs, shapes and number of blades for a windmill, but have more or less finalized on a three blade design now.
Windmills can be horizontal axis or vertical axis, though the horizontal axis windmills are most common.
Working of a Windmill
Windmills harness wind energy. Typically, this energy is ultimately converted to electrical energy. Today's windmills are computer controlled. The main task of the computer is to keep the windmill facing the wind, so that it is able to gain maximum benefits of the prevailing air currents. To achieve this objective, the computer monitors the direction and speed of the wind using instruments on top of the windmill. The computer analyses this data and manipulates the windmill hub so that the blades are always facing into the wind. The blades themselves are optimized to rotate at maximum speed.
Components of the Windmill
A windmill typically consists of the blades, the hub and the machinery that is housed in the hub to harness the winder energy. The rotor has blades attached to the hub. The nacelle is a windmill component that houses a drive train consisting of a gearbox, connecting shafts, support bearings, the generator, etc. All these components are mounted on the windmill tower.
The Windmill Hub
The windmill hub is the joint where the blades of the windmill join. It also houses the mechanical components that make the blades rotate. The windmill hub is one of the most crucial components of the windmill. It not only bears the forces and moments produced by the blades, it also transfers the torque generated to the shaft of the mainframe assembly. In addition, the windmill hub must also bear the weight of the blades and their bending moment too.
Windmill Hub Casting Manufacturers
The size of steel castings for large turbines, especially the blade hub units, is a daunting task for windmill hub manufacturers, more so if the blades are designed for pitch control. Since casting of windmill hubs is an intricate task, most windmill manufacturers of repute prefer to outsource it to reliable manufacturers. Windmill hubs are typically cast in steel, or alloys of steel and aluminium. Manufacturers from India and China are major players in the manufacturing of windmill hub. This is because they have the expertise to cast the hubs and are relatively less expensive.