5.4 ENVIRONMENTAL IMPLICATIONS

5.4.1 Emissions

5.4.1.1 Energy payback

The amount of energy required to construct a complete wind turbine is recovered in the electricity generated typically after about 3 months of full power operation. Wind power is one of the most competitive energy sources in this respect.

5.4.1.2 Zero greenhouse

Normal operation of a wind turbine generates no CO₂ or other 'greenhouse gas'. Such emissions can only normally arise from the energy input required for its original construction, with a little for installation, commissioning and maintenance.

5.4.2 Visual

Public attitudes to the appearance of large wind turbines vary very widely. Planners should certainly exercise some sensitivity to their placement in the landscape, for instance to avoid their domination of the countryside in such places as national parks. Many people consider wind turbines to have a beauty of their own and to represent hope for the future of the planet, while others regard them as an intrusion of industrial machinery onto the natural skyline. Some public opinion surveys have shown that those living near a wind farm are more likely to support their development than those living further away (ref 5.4). A 1994 survey in Wales showed that an initial 41% approval of local wind farms before construction was converted into 66% afterwards (ref 5.5). Although such surveys also reveal a much wider overall range of opinion (e.g. ref 5.6), both of these suggest that the anticipation may be worse than the reality! Offshore sites are certainly expected to be less controversial in visual terms since towers will generally be several km from the shore.

5.4.3 Noise
Early wind farms were said to be noisy by a few local inhabitants, and this received widespread publicity in the UK. As far as overall noise level is concerned, it has been demonstrated that wind turbines are no louder than the wind noise normally generated by trees or buildings. It is perfectly possible to stand underneath a turbine and have a normal conversation without raising your voice. Some of the noise objections referred to a persistent tone, which may have come from a gearbox; gearboxes have certainly been improved, and the nacelle is now acoustically insulated to minimise any such irritating constant frequency. Rotors in Europe are normally positioned upwind of the tower, which minimises any cyclic pulse effect, and the blades are also designed to minimise any aerodynamic swishing noise. It seems to be generally agreed that noise is no longer much of an issue.