Electricity from Wind

Modern windmills are called wind turbines and are installed in large groups are called wind farms to take advantage of natural wind corridors, some of which are actually off shore. Turbines produce about forty percent of all electricity on earth, but are usually driven by steam heated by the burning of fossil fuels or the application of nuclear fission. Wind powered turbines are an attractive alternative because they produce zero emissions and use a fuel source that is entirely renewable. But no matter how they're powered, turbines are connected to generators which induce the movement of electrical potentials existing within transmission wires. Turbine-driven generators, which use motion to produce electricity, are essentially the opposite of motors, which use electrical energy to produce motion.

Individual wind turbines can generate about 100 kilowatts of energy -- turbine farms can create several megawatts. The world's largest wind farm, in Texas, has 421 can power 220,000 homes per year. The major drawbacks to wind energy have been the cost of producing and maintain wind farms, and the limitations created by a reliance on wind. Over time, however, technology has improved the efficiency of wind turbines, making it a cost effective enterprise for producers and consumers alike. Though it's unlikely wind power could ever meet all of humanity's electricity need, it has become a viable part of a diversified energy generation prof

Horizontal Axis Wind Turbine (HAWT)

A wind turbine in which the axis of the rotor's rotation is parallel to the wind stream and the ground. All grid-connected commercial wind turbines today are built with a propeller-type rotor on a horizontal axis (i.e. a horizontal main shaft). Most horizontal axis turbines built today are two- or three-bladed, although some have fewer or more blades. The purpose of the rotor is to convert the linear motion of the wind into rotational energy that can be used to drive a generator. The same basic principle is used in a modern water turbine, where the flow of water is parallel to the rotational axis of the turbine blades.

The wind passes over both surfaces of the airfoil shaped blade but passes more rapidly over the longer (upper) side of the airfoil, thus creating a lower-pressure area above the airfoil. The pressure differential between top and bottom surfaces results in aerodynamic lift. In an aircraft wing, this force causes the airfoil to rise, lifting the aircraft off the ground. Since the blades of a wind turbine are constrained to move in a plane with the hub as its center, the lift force causes rotation about the hub. In addition to the lift force, a drag force perpendicular to the lift force impedes rotor rotation. A prime objective in wind turbine design is for the blade to have a relatively high lift-to-drag ratio. This ratio can be varied along the length of the blade to optimize the turbine's energy output at various wind speeds.