It is difficult to get comprehensive data on wind farm performance as it is shielded from view by “protection of competitive data” or by contract terms. A new study bearing comprehensive data from Scotland confirms what skeptics have been saying about windfarm performance. This new study is perhaps the most comprehensive since the Bentek Energy(an energy analytics firm) study of Colorado and Texas windfarms.
Stuart Young Consulting with support from the JOHN MUIR TRUST (emphasis mine, to highlight that this study was commissioned by a green NGO) 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.
This report examined 5 common claims by the wind industry and the Scottish Government. The five claims are in RED with the actual result in BLACK:
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.
The final claim about “pumped storage” varies with the area where the windfarms are located. In the US, an area such as the Great Plains, where wind availability is favorable to siting of windfarms, has little to no pumped storage hydro capacity available. Availability in most other areas is either used or would be difficult to develop as environmental groups object to the use of dams. Further there is a loss of efficiency when the windpower electricity is used to pump water to some higher elevation and then recovered in hydroelectric turbines.
The author of the report 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.”
To see the John Muir Trust posting in more detail, click here
For further information on the Bentex study mentioned at the begining of this posting click here.