Wind Power and Wind Turbine Designs

Wind power is the use of the wind to do useful work, today chiefly to generate electricity. It is a renewable source of energy, because the wind is driven by the heating of the atmosphere by the Sun and is continually replenished. Windmills once harnessed the wind mainly to grind grain or pump water; modern wind turbines instead drive electrical generators, and large numbers of them are often grouped together in wind farms on land or offshore.

Wind turbines fall into two broad families defined by the orientation of their rotating shaft. The familiar horizontal-axis turbine has propeller-like blades on a horizontal shaft at the top of a tall tower and must turn to face the wind; most large commercial turbines are of this kind. Vertical-axis turbines spin about an upright shaft and accept wind from any direction without needing to be turned. Two classic vertical-axis designs are the Savonius rotor, which is dragged around by curved scoops, and the Darrieus rotor, whose curved aerofoil blades use lift to turn at higher speeds.

The choice of design reflects trade-offs in efficiency, size and the conditions where the turbine is used. Horizontal-axis machines generally capture more energy and dominate large-scale generation, while compact vertical-axis turbines can suit turbulent or built-up sites. Wind energy produces electricity without burning fuel or releasing carbon dioxide in operation, though it varies with the weather, which is why it is usually combined with other sources to give a steady supply.

Frequently asked questions

What is the difference between horizontal- and vertical-axis turbines?

A horizontal-axis turbine has propeller-like blades on a horizontal shaft and must face the wind, while a vertical-axis turbine spins about an upright shaft and accepts wind from any direction.

What are Savonius and Darrieus turbines?

They are vertical-axis designs. The Savonius uses curved scoops dragged round by the wind, while the Darrieus uses curved aerofoil blades that generate lift to spin faster.

Why is wind power considered renewable?

The wind results from the Sun heating the atmosphere and is constantly replenished, so using it does not deplete the resource.