Wind power

Wind power is created by the conversion of kinetic energy in wind, which is the energy of the moving air molecules, to energy in the form of electricity.

Types of wind power

Wind power technology differs by whether the shaft that transfers rotational energy from the blade to the generator is mounted horizontally or vertically. The most common is the horizontal axis. Less common is the vertical axis.

Technology also differs by whether the wind turbine is installed on land (onshore), or in a body of water (offshore). Offshore projects use the horizontal axis and other turbine technology similar to large onshore installations, but they are built on a platform.

How wind power works

The kinetic energy in wind is converted to rotational mechanical energy by rotor blades connected to a shaft. The rotor blades spin when the wind speed hits an appropriate level, which in turn causes the shaft to spin. In most cases, the slowly rotating shaft is connected to a gearbox inside a housing called a nacelle. The gearbox increases the rotational speed of the shaft for spinning a generator (or generators) that converts the mechanical rotation into electricity. In other cases, the gearbox is eliminated and the generator is directly connected to the shaft driven by the blades.

Depending on the type of generator, the generator itself may produce AC power synchronized to the frequency of the transmission system; "wild" AC power at a frequency that changes with the speed of blade rotation; or DC power. In the last two cases, an inverter and/or other devices may be required to condition the power and convert it to a form the grid can use.

The electricity from the generator flows through cables to a transformer that raises the voltage to transmission levels. The power then flows onto the transmission line. Vertical-axis turbines work similarly except that the gearbox and generator are usually located on the ground rather than on a tower.

Wind generation can be centralized or distributed. Most commonly wind is centralized, which is also called utility-scale wind. This includes onshore and offshore projects. In some cases, onshore wind is connected to the distribution system or located at a customer facility, in which case it is called distributed wind.