Wind power is one of the simplest ideas in energy: moving air pushes on blades, the blades turn a shaft, and a generator turns that rotation into electricity. The details are where it gets interesting, and they explain why some places are far better suited to wind than others. This page covers the essentials without jargon or statistics.
What happens inside a turbine
A modern turbine's blades are shaped rather like aircraft wings. As air flows past, the difference in pressure on either side of each blade creates lift, which turns the rotor. The rotor connects to a generator housed in the nacelle, the box at the top of the tower. Some designs use a gearbox to speed up the rotation; others use generators built to work directly at slower speeds. Sensors constantly track the wind's direction, and the whole nacelle turns to face it. In very strong winds the blades are angled away, or the turbine stops, to protect the machine. For a closer look, see How a Wind Turbine Works.
Why wind speed matters so much
The energy carried by the wind rises very steeply as the wind gets faster. A site where the wind is only a little stronger on average can produce a great deal more electricity than a calmer one. That is why developers spend so long measuring the wind before building anything, and why a breezy coastline or ridge is valued so highly.
Why height matters
Near the ground, trees, buildings and uneven terrain slow the air and make it turbulent. Higher up, the wind tends to be stronger and steadier. Taller towers and longer blades reach that better wind and sweep a larger area, which is one reason turbines have grown so much over the years.
Capacity versus output
A turbine's capacity is the most power it can produce when the wind is ideal. Its output is what it actually generates over time, which depends on how often and how strongly the wind blows. The two are easily confused in headlines. A wind farm rarely runs at full capacity for long, and that is normal: what matters is the total energy produced across a year and how well it fits with other sources on the grid.
Onshore and offshore
- Onshore turbines stand on land. They are generally easier to build, reach and maintain, but they must fit around homes, farms, wildlife and landscapes.
- Offshore turbines stand in the sea, where winds are often stronger and steadier and there is more space. The trade-offs are harsher conditions, more complex foundations and the need for undersea cables to bring power ashore.
Where to go next
To understand how wind data is presented, read How to Read a Wind Map. To see how a project moves from measurement to operation, try Projects Explained. And for a local example of a famously persistent wind, meet the Cape Doctor, Cape Town's south-easter.