Analysis of UK Wind Power Generation November 2008 to December 2010

Published: 31st March 2011

Stuart Young Report: detailed analysis of windfarm output in Scotland

In recent years, with wild land coming under pressure from industrial-scale developments, the Trust has grown increasingly concerned at the rate and scale of loss, and our subsequent inability to defend landscapes within the planning and development process. In order to take the best decisions for wild land, we need to look at the evidence to better understand the real costs and benefits.

In 2011, when the Trust heard about Stuart Young’s painstaking research analysing publicly available data on the generation from National Grid-monitored wind developments in the UK, we were interested to see his results. His report shows that some key assumptions for wind developments are falling short of expectations. We hope the evidence in the report will lead to a more open, honest and informed debate about large-scale, industrialised wind power, and remind people what is at risk when these developments are located in wild land areas.

The report "Analysis of UK Wind Power Generation November 2008 to December 2010" (see downloads below) is the result of detailed analysis of windfarm output in Scotland over a 26-month period between November 2008 to December 2010 using data from the BMRS (Balancing Mechanism Reporting System). It was the first report of its kind and draws on data freely available to the public. This data challenges five common assertions made regularly by wind industry and the Scottish Government that:-    Wind turbines will generate on average 30% of their rated capacity over a year

  •     The wind is always blowing somewhere
  •     Periods of widespread low wind are infrequent
  •     The probability of very low wind output coinciding with peak electricity demand is slight
  •     Pumped storage hydro can fill the generation gap during prolonged low wind periods

In fact, the report finds that:-

  • On 124 separate occasions from November 2008 to December 2010, the total generation from the windfarms metered by National Grid was less than 20MW (a fraction of the 450MW expected from a capacity in excess of 1600MW+). These periods of low wind lasted an average of 4.5 hours.
  • Actually, low wind occurred every six days throughout the 26-month study period. The report finds that the average frequency and duration of a low wind event of 20MW or less between November 2008 and December 2010 was once every 6.38 days for a period of 4.93 hours.
  • At each of the four highest peak demand points of 2010, wind output was extremely low at 4.72%, 5.51%, 2.59% and 2.51% of capacity at peak demand.
  • In fact, the average output from wind was 27.18% of metered capacity in 2009, 21.14% in 2010, and 24.08% between November 2008 and December 2010 inclusive.
  • The entire pumped storage hydro capacity in the UK can provide up to 2788MW for only 5 hours then it drops to 1060MW, and finally runs out of water after 22 hours.

The report also found that during the study period, wind generation was:

  • below 20% of capacity more than half the time
  • below 10% of capacity over one third of the time
  • below 2.5% capacity for the equivalent of one day in twelve
  • below 1.25% capacity for the equivalent of just under one day a month

At the moment, the rapid expansion of wind farms represents the biggest threat to our remaining wild land. Wild land helps to sustain human life as well as plant, bird and animal life. Our wild landscapes provide the foundation for our tourist industry. That's why we're concerned about emerging questions regarding the efficiency and environmental impact of large-scale wind power developments, and about the proportion of our energy that they’re intended to supply. If wind is not delivering adequately, it will be a pointless sacrifice of Scotland’s natural assets.

The report can be downloaded below. Low Wind Events - see Appendix D of report. The Master Spreadsheet is available on request.