Wind Turbines: How They Work and the Different Types
A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. But how do wind turbines generate electricity?
In basic layman's terms, a wind turbine works the opposite of a fan: instead of using electricity to make wind, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and thus makes electricity. Sounds simple, doesn't it? We found a pretty easy to understand, animated set of diagrams on the democratandchronicle.com site (even with narration) that demonstrates the process that a typical wind turbine uses to produce electricity.
There are two main kinds of wind turbines (also called wind generators, wind power units (WPU), wind energy converters (WEC) or aerogenerators); they are separated into two types based on the axis in which the turbine rotates, namely those with vertical axis, and those with horizontal axis rotation. The more commonly used design for a wind turbines is the horizontal axis turbine, where the main rotor shaft and generator are at the top of a tower. Smaller turbines are held by a simple wind vane, but larger turbines use a wind sensor coupled with a servo motor. A horizontal axis turbine must be pointed towards the wind to be effective, because the tower generally creates turbulence behind it.
The second but less utilized primary type of wind turbine is called the vertical axis turbine. This design has the main rotor shaft arranged vertically in its axis. A key aspect of this design is that a servo motor is not required for tracking because it can catch wind from any direction (advantageous if the area is noted for inconsistent wind direction). The primary advantage of this arrangement over the horizontal turbine design is that the turbine does not need to be pointed into the wind to be effective. Another advantage of this design is that the generator is placed on the ground, making maintenance easier. However, this design creates a lot of torque, meaning that it produces less electricity than a similarly sized horizontal axis turbine.
Of course, there are many different variations of wind turbines both amongst the two major types as well as many unique specialized wind turbines. We found a site www.thewindpower.net which provides excellent photos of many of these and a brief description of each.
Modern wind turbines are equipped with high-tech computers and power electronics that process over 200 types of data, from wind speeds and oil temperature to voltage dips on the grid. “Smart” wind turbines can help make the electricity transmission system more reliable.
As far as variation of size for wind turbines, utility-scale turbines range in size from 100 kilowatts to as large as several megawatts. Larger turbines are grouped together into wind farms, which provide bulk power to the electrical grid. Single small turbines, below 100 kilowatts, are used for homes, telecommunications dishes, or water pumping. Small turbines are sometimes used in connection with diesel generators, batteries, and photovoltaic systems. These systems are called hybrid wind systems and are typically used in remote, off-grid locations, where a connection to a utility grid is not available.