How Is Wind Energy Used to Generate Electricity?

With the cost of producing energy projected to continue rising, and pollution becoming a serious environmental problem, finding renewable sources of cheap and clean energy has become an important industry. Wind energy has long been considered one possible source of renewable energy, but has made its biggest advances in the last 20 years. By 2001, over 2,000 megawatts of wind energy capacity was added in the U.S. and this capacity continues to increase today.

Turbines

• Wind turbines work the opposite of a fan. Instead of using electricity to create wind like a fan, the wind is used to turn a fan and create electricity. Since the wind is produced by the effects of the sun heating the atmosphere, the wind is actually a form of solar energy, so in effect wind energy is solar energy. Turbines harness this energy by using the force of the wind blowing against them to turn a central axle.

Operation

• To harness wind energy, a fan, or more accurately a turbine, is mounted on a long pedestal. The turbine is connected by gears to a shaft, which is in turn connected to a generator. As the wind pushes against the turbine it causes it to turn. This motion is transferred to the shaft, which turns the generator to produce electrical energy. Two types of turbines are used in this manner.

Types

• The most common type of wind turbine is the horizontal axis turbine. This turbine most closely resembles a traditional fan or propeller design having vanes that are mounted horizontally on a central axis. The second type is a vertical axis turbine, which uses vanes mounted vertically in series or parallel around a central axis. These vanes operate on the same principals as an airplane wing, and when wind passes over them they create lift. This lift is harnessed as force, which causes the vanes and the axle they are attached to to spin around a central axis. The axle is connected to a shaft, and the rest of the process is the same as with a horizontal turbine. These vertical turbines are much less efficient than horizontal turbines, and are more useful for creating mechanical force rather than electrical power.

Methods

• Wind energy is not constant. Because of this wind turbines cannot produce a steady supply of electrical energy. In order to increase the efficiency and practicality of wind turbines, power must be used immediately or stored for later use. In large scale wind farm operations where many turbines are arranged in series to produce large amounts of electrical power, electrical energy from the wind turbines is sent directly to the normal electrical grid that supplies electricity to the surrounding area. In small applications such as single home wind turbines, energy from the wind turbine is used to power the home while also charging batteries for periods when wind activity is too low to provide sufficient energy.

Efficiency

• Wind turbines produce no pollutants and use no non-renewable energy sources to create electricity, so efficiency is an approximate value. Turbine efficiency is determined by how well it converts wind energy to electricity. How well a turbine converts wind energy to electrical energy is determined by the size of the turbine, the size of the blades, the density of the air, and how fast the air is moving. The physics behind wind energy efficiency limit how much total energy a turbine can extract from the wind. Betz's law says that a wind turbine can only extract up to 59 percent of the energy from the wind, so the closer a turbine comes to reaching that percentage, the more efficient it is.