//Generatng Electricity from Thin Air

Generatng Electricity from Thin Air

Why are wind turbines so tall? How do the blades turn to catch the wind as it changes direction? Can
there ever be too much wind? Find out the science behind this renewable energy source from two BP
wind engineers – this is how electricity is generated out of thin air.
All of the turbines are between 80 and 100 metres tall, and the rotor diameters are larger than the
wingspan of an Airbus A380 (80 metres), so these are really large machines. The towers are built this tall
because there is more wind to be found higher off the ground, and the longer the rotor blade, the more
wind it can capture and the more energy it can create.
The blades work best when they are facing the wind and, in order to keep them turned towards the
wind, each nacelle is equipped with at least one anemometer – a device that senses wind direction and
speed and then applies a transfer function. This process activates a motor that turns the nacelle towards
the wind.
The anemometer also regulates the pitch of the blades to capture the most wind possible, and it stays
that way until the turbine reaches its rated power – the maximum capacity of a turbine to produce
electrical power. The nacelle controllers then change the pitch of the blades so that the straight edge
faces the wind in a process called feathering. This prevents the blades from catching the wind and
rotating, since too much wind can actually damage the turbine. Therefore, when the turbine reaches
maximum speed, it shuts down.