How does a wind farm work?
Wind turbines generate electricity by harnessing the natural force of the wind in
order to power an electrical generator.
Almost all the wind turbines that produce electricity consist of a rotor with blades
that turns on a horizontal shaft; the latter is connected to a mechanical transmission
assembly or gearbox and, finally, to an electrical generator, both of which are located
in the nacelle mounted at the top of the mast.
The main components of a wind turbine are:
- Rotors.
- Usually 3 blades on the rotor.
- Blades made of fibreglass with polyester or epoxy reinforcements.
- Operation with constant or variable rotor speeds.
- Automatic power control depending on wind speed, with cut out at very high speeds
(mechanical safety): by means of the angle of the blade (pitch) or its own aerodynamics
(stall).
- Widespread use of gearboxes and, in certain cases, of direct shaft-generator transmission.
- Automatic positioning (yaw) according to variable wind direction (sensors for monitoring).
- Tubular towers made of steel and generally painted in light grey.
The power of wind turbines installed on land varies from several hundred kilowatts
up to two and even three megawatts, with the crucial parameter being the diameter
of the turbine: the greater the length of the blade, the greater the area swept and
the energy produced. At present, the average power of the machines currently being
installed is close to 1,000 kilowatts, but it is becoming increasingly more common
to install machines of 2 MW and even higher.
The energy produced by a wind turbine varies in terms of the actual potential of
the site itself (cube function of the wind speed)), of the availability of the machine
itself (ability to operate in the presence of wind: with the standard being above
98%) and the arrangement of the devices in the wind farm (wake effect: negative effect
on each other).
Although still at an experimental stage, wind farms are starting to be built in the
sea ("offshore"), various kilometres off the coast, in order to minimise their environmental
impact and, above all, make the most of the better wind conditions given the disappearance
of the negative effect caused by the terrain.
These installations are equipped with much more powerful machines, with development
currently underway on prototypes of up to 5 MW. Specific conditions are required
on the seabed in order to render the execution of the foundations or support systems
technically and financially viable.
