YOUR correspondents Fiona Stark (Letters, September 4) and Linda Holt (Letters, September 5) are correct to highlight the absence of full data on wind turbine numbers in Scotland.

Most seriously, there has been a deafening silence from Holyrood about the potential numbers of turbines and how much of our countryside they would cover.

Alex Salmond has produced no figure for the number of turbines required to meet his target of 100% of Scotland's electricity from renewables. However, to estimate this requires only simple arithmetic.

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In 2012 there were, approximately, 1400 wind turbines in Scotland, producing about 20% of our electricity, along with another 20% from hydro. Since there is no prospect of significant new hydro capacity, the remaining 60% would have to come from a further 4200 turbines.

Since large turbines must be spaced about 500m apart, one can only get four per square kilometre, so the total of 5600 would occupy around 1400 square kilometres.

The combined areas Edinburgh and greater Glasgow is 627 square kilometres. The total area of Scotland classified as urban is 1465 square kilometres.

Jack W Ponton,

Old Cottage Gardens,