Blowing foul

Here's another twist to the windy tale. Wind farms produce far less energy than previously claimed, according to a new report. Wind-energy output at wind farms metered by the UK’s National Grid was less than 10% capacity for one third of the time during the two-year study. For numerous extended periods of time all the wind turbines linked to the National Grid muster less than 20MW of energy: enough power for 6,667 households to boil their kettles for a cup of tea.

Low output also sometimes coincided with periods of peak demand. The report, supported by Scottish conservation charity the John Muir Trust, said wind "cannot be relied upon" to provide any significant level of energy generation at any defined time in the future.

It also called into question common assertions made by industry such as that wind turbines will generate on average 30% of their rated capacity over a year.

The study challenged assertions by industry and government such as that periods of widespread low wind are "infrequent". It found that the average frequency and duration of a low wind event of 20MW or fewer was once every 6.38 days for a period of 4.93 hours.

The study also found that at each of the four highest peak demands of 2010 wind output was low, being respectively 4.72%, 5.51%, 2.59% and 2.51% of capacity. Wind generation was below 20% of capacity for more than half the period of the study.

Well, one can contest that this is the story for Scotland alone. Really?