Sir,

Once again we have a propaganda coup for PSEEG and the advocates of wind power. How ironic that the day chosen for the visit to Castle Pill should be September 24, when there was almost no wind. Many of those invited to gather may not appreciate that the output of a wind turbine drops dramatically with wind speed.

The claimed performance for these machines is only available at wind speeds of Force 7, 8 or 9 (14 - 24 metres per second). As the wind speed drops below 14 M/s, the output falls dramatically - at 3.5 M/s it would be less than two per cent of the maximum. If the wind on that day was blowing at 3 M/s, it would not be enough to rotate the blades, let alone generate any useful amount of electricity.

Perhaps Janet Roberts can confirm that the turbines were not actually consuming electricity to rotate them and how much electricity was being supplied to the grid on that day.

The other aspect of this story was the ludicrous use of a sound meter to demonstrate how quiet the turbines were. The nuisance sound experienced by people who live near wind turbines is a very low frequency throb. This travels some distance depending on the wind speed and the topography of the landscape. It is very often not heard close to the turbine and certainly would not be a problem during light winds, when the blades are barely turning.

Wind turbines are heavily subsidised by all of us and are not a substitute for other forms of power generation, as they only produce electricity when the wind blows strongly, not to match demand. All of the turbines existing and planned for the UK will not make a measurable impact on global warming.

R Duffield,

BSc MIChemE CEng,

Saundersfoot.