Wind power is generated by capturing the kinetic energy of wind and converting it into electrical energy by a turbine. Turbines are of two types: Vertical-axis wind turbines (VAWTs), and horizontal-axis wind turbines (HAWTs). HAWTs are more common in the wind power generating industry.
Any turbine used in wind power generating possesses three essential functional parts: rotor blades, shaft, and a generator. The rotor blades capture kinetic energy of the wind and transform it to shaft rotational energy. The shaft in turn channelizes the energy to the generator. A particular wind turbine is built specifically to tap the wind energy present at that particular location.
Each horizontal axis wind turbine or HAWT consist of the following functional parts:
» Rotor blades
» Shaft
» Nacelle
» Tower
» Electrical equipment
The nacelle is the casing that contains the generator, electrical control unit, gearbox, brakes, and yaw controller. The yaw controller actuates the rotor to align the unit with the wind direction. The gearbox controls the shaft speed between generator and rotor hub.
Wind power employs modern turbine aerodynamics to extract maximum electrical energy from wind flow. The turbine blades follow an airfoil design. The lift and drag aerodynamic forces play a vital role in the electrical energy generating process. The efficiency of the machine unit depends upon the length of the blade- the greater the length, the more electrical power generating capacity. Wind power generation is also dependent on the tower height. The optimal wind speed is 33 miles per hour.
Excess wind speed is detrimental to wind turbine power generation. Turbines cease to operate above wind speeds of 45 miles per hour.
A number of safety mechanisms are present to turn off the turbine in times of extreme wind speeds. Modern wind turbines employ 3 types of braking systems: Passive stall control, Active stall control, and Pitch control.
The Pitch control is activated through an electronic controller that regulates the machine's power output. The controller instructs the blades to be unaligned with the wind in times of high wind speed. The blades in Active stall control systems are pitchable.
The Passive stall control system incorporates blades mounted at a fixed angle. The blades themselves apply the brakes at high speeds.
Commercial wind power is generated in large wind farms. The wind turbines commonly used in wind farms have rated power capacities between 700kW and 1.8 MW. More than 50 wind turbines are grouped together for maximum power generating capacity. The largest wind farm is the Raheenleagh Wind Farm in Ireland. The wind farm is located off the Irish coast.