Stuart Young Consulting, with support from the John Muir Trust, has released a report studying the ability of wind power to make a significant contribution to the UK's energy supply. It concludes that the average power output of wind turbines across Scotland is well below the rates often claimed by industry and government.
Indeed, for numerous extended periods of time all the wind turbines in Scotland linked to the National Grid muster less than 20MW of energy - that's enough power for a mere 6,667 households to boil their kettles for a cup of tea.
Helen McDade, head of policy at the John Muir Trust, the U.K.'s leading wild land conservation charity, said: "This report is a real eye opener for anyone who's been wondering just how much power Scotland is getting from the fleet of wind turbines that have taken over many of our most beautiful mountains and hillsides. The answer appears to be not enough, and much less than is routinely claimed."
Stuart Young, author of the report, said, "Over the two-year period studied in this report, the metered windfarms in the U.K. consistently generated far less energy than wind proponents claim is typical. The intermittent nature of wind also gives rise to low wind coinciding with high energy demand. Sadly, wind power is not what it's cracked up to be and cannot contribute greatly to energy security in the UK."
Mr. Young said: "It was a surprise to find out just how disappointingly wind turbines perform in a supposedly wind-ridden country like Scotland. Based on the data, for one third of the time wind output is less than 10% of capacity, compared to the 30% that is commonly claimed.
At the end of the period studied, the connected capacity of wind power was over 2500MW so the expectation is that the wind network will produce, on average, 750MW of energy. In fact, it's delivering far less than everyone's expectations. The total wind capacity metered now is 3226MW but at 3a.m. on Monday 28th March, the total output was 9MW."
The report, Analysis of UK Wind Generation, 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's the first report of its kind, and drew on data freely available to the public. It challenges five common assertions made regularly by wind industry and the Scottish Government:
1. 'Wind turbines will generate on average 30% of their rated capacity over a year'
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.
2. 'The wind is always blowing somewhere'
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 1600 MW). These periods of low wind lasted an average of 4.5 hours.
3. 'Periods of widespread low wind are infrequent.'
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.
4. 'The probability of very low wind output coinciding with peak electricity demand is slight.'
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.
5. 'Pumped storage hydro can fill the generation gap during prolonged low wind periods.'
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.
Read the Executive Summary or downloaded the Full Report. Supporting Information is also available:
 BMRS (Balancing Mechanism Reporting System) The source of the information on which this analysis is based is the Historic Generation by Fuel Type Data Files on the ELEXON Portal website. Registration is required to create an account.
ELEXON Ltd is the Balancing and Settlement Code Company (BSCCo) defined and created by the Balancing and Settlement Code (BSC and also known as the Code). ELEXON Ltd procures, manages and operates services and systems, which enables balancing and settlement of the wholesale electricity market and retail competition in electricity supply.
A wealth of information is to be found on the Balancing Mechanism Reporting Service (BMRS) website at www.bmreports.com from where links to related sites are found.
Stuart Young and the John Muir Trust are grateful to ELEXON Ltd for permission to use its generation data, and for the not inconsiderable help I have had from the BSC Service Desk. BSCServiceDesk@logica.com.