On studying the article ‘Race for renewables’ in the June 2012 issue of PE I have the following comments to make.
It is stated at the bottom of the first page that ‘wind turbines have an efficiency of about 25%’ and a sentence later the question is posed ‘What are we going to do the other 75% of the time when the wind doesn’t blow?’.
The efficiency of a wind turbine depends upon the proportion of the supply rate of kinetic energy of the air encountering the turbine blades which becomes work. It has nothing to do with how frequently the wind blows.
Dr John Jones, Aberdeen