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Wind

Wind energy is ample, renewable, widely distributed, clean and mitigates the greenhouse effect if used to replace fossil-fuel-derived electricity. Wind energy is used both for supplying power to the national electrical grid and for providing electricity to rural residences or grid-isolated locations.

How it Works

The wind spins the blades, making them turn a shaft inside the nacelle (the box at the top of the turbine) which, through a gearbox, increases the rotation speed enough to action a generator, which uses magnetic fields to convert the rotational energy into electrical energy.

The power output goes to a transformer, which converts the electricity from the generator at around 700V to the right voltage for distribution system, typically 33kV.

Site Layouts

The ideal location for a large (above 1MW) wind turbine is >70mt above any surrounding object within about a 1.5 km radius. Surface of chosen sites should be either flat or very regular, with limited constructions and woods around. Alternatively, the turbines could also be located on hills’ ridges, ideally oriented perpendicularly to the main-wind axis.

The land necessary for erecting a large wind turbine is circa 3 ha in surface and the sites chosen should have at least 6 m/sec of average wind speed. As the power available from the wind is a function of the cube of the wind speed, if the wind blows at twice the speed, its energy content will increase eight-fold. It imports that turbines installed at a site where the wind speed averages 8 m/s produce 75-100% more electricity than those where the average wind speed is 6 m/s.

The Technology

Instruments to measure the wind speed and direction are fitted on top of the nacelle. When the wind changes direction internal electrical motors turn the nacelle and the blades along with it, to face the wind. The nacelle is also fitted with automatic brakes, so that the turbine can be switched off in very high winds to prevent damages. All information concerning ambient and technical function of the turbine is recorded by computers and transmitted to a remote control center.

Environmental Aspects

Wind turbines provide several positive environmental benefits:

  • reduce atmospheric carbon dioxide emissions by reducing the need for combustion of fossil fuel sources
  • can be installed and be functioning without disrupting normal agricultural activities
  • with careful planning, there is minimal negative impact on wildlife and natural habitat

Wind turbines are rather quiet. A typical wind farm 350m away has a sound pressure level (noise) of 35-45 decibels (dB), in comparison with a rural night time background (20-40dB), a jet aircraft 100m away (120dB) or a busy office environment (60dB). Even so, wind turbine engineers and designers are continuously reducing noise by good turbine blade geometry design which can lead to reduction in aerodynamic noise level by as much as 4dB.

For building the wind turbines, experienced biologists and local agencies carefully assess impact on local flora and fauna, for instance for minimizing potential issues with avian populations.

It is important for wind turbines to blend in well with the background color of their surroundings. For instance, the outer gel-coat of the blades is painted with a matt finish to minimize reflections.