As regards their operating principle, contemporary wind farms closely resemble windmills, known to humanity for 2,500 years. Their wind-driven blades once propelled grist mills, sawmill equipment and drainage pumps. Modern wind turbines, often grouped in wind farms, generate eco-friendly electricity, which is subsequently distributed to households and industrial customers.
A wind turbine consists of several basic elements:
- a tower designed to mount a turbine at a considerable height, where wind gusts are much stronger;
- a moving nacelle which allows to adjust the turbine position so that it matches the direction of wind. The 360-degree rotation is possible thanks to a motor and gearbox installed at the top of the tower. Moreover, the nacelle houses a generator and control systems for all equipment;
- a rotor thanks to which the kinetic energy of wind is converted into mechanical energy. Typically, a rotor consists of three blades set on an axis (however, rotor designs comprising two or more blades are also available).
The blowing wind causes a difference in pressure in front of and behind the blades, as a result of which the turbine starts to rotate. The rotor powers the generator (placed typically in the nacelle), which converts the mechanical energy into electricity. The blades of a wind turbine rotate at a speed of 15-20 rpm. A standard induction generator used by such plants is able to generate electricity at a speed of over 1,500 rpm. Therefore, an appropriate gearbox needs to be in place to increase the rotational speed. The gearbox is located between the axis of the rotor and the generator.
More advanced systems employ mechanisms allowing to change the rotor pitch angle.
In order to generate electricity in commercial quantities, wind farms, comprising a cluster of wind turbines, are built. The EW Kamieńsk Wind Farm, owned by PGE Energia Odnawialna S.A., is one of the most picturesque and widely known examples of such generation assets in Poland.