Wind turbines are 25 per cent less effective than the renewable energy industry claims, according to research.
The John Muir Trust (JMT), one of Scotland’s leading conservation bodies, has challenged the common assertion that wind farms run at an average of 30 per cent capacity over a year.
A study carried out for the Trust into the energy generated by dozens of wind farms, the majority of which are in Scotland, between November 2009 and last month, found they actually ran at 22 per cent of capacity.
Campaigners insist the figures, drawn from data provided by the National Grid, challenge the role of wind farms as an efficient source of renewable energy.
They said hundreds of wind farms had secured planning permission across Scotland based on inaccurate assumptions of their output.
“This analysis shows that over the course of a year, the average load factor fell well short of what the industry claims, yet the 30 per cent figure is peddled at every public inquiry into a proposed wind farm,” said Helen McDade, head of policy at the JMT. “This data is needed to counter that hype.”
The JMT examined the performance of 47 wind farms capable of producing 2,430 megawatts (MW) of green energy. They include Whitelee wind farm, near Glasgow, which comprises 322 turbines, and the 164-turbine Crystal Rig 2 development in East Lothian. Apart from Burbo Bank, Barrow and Thanet, which are offshore sites south of the border, all of the wind farms are in Scotland.
The research found over 395 days, the wind farms could have produced 17,586,000 MW hours of energy running at full capacity. In reality, 3,881,900MW hours was generated, equivalent to 22.07 per cent.
And over the past two years, wind generation across the sites fell below 20MW on 123 separate days for a combined duration of 25 days. For a total of nine days, output dipped below 10MW, barely enough power to boil 3,300 household kettles.
The website of RenewableUK, which represents about 650 wind and marine companies, states that over a year, a turbine will generate about 30 per cent of the theoretical maximum output.
“This is not a snapshot of wind energy output, it is a robust appraisal over a significant period of time,” said Stuart Young, who was commissioned to investigate wind power by JMT. “It doesn’t matter how many wind farms you build, if the wind isn’t blowing, the blades aren’t turning.”
Niall Stuart, chief executive of Scottish Renewables, which represents renewable energy companies in Scotland, said the winter of 2009/10 was one of the calmest on record and that it was “no surprise” output figures for the year were below average.
He said: “It’s well understood that there are variations within and between years, but no form of electricity works at 100 per cent capacity 100 per cent of the time.”
A spokesman for the Scottish government said it was on track to exceed a target of meeting 31 per cent of electricity demand from renewables by 2011. He said wind energy would play a part in hitting an 80 per cent target by 2020.
“Our approach to low-carbon electricity is broad and includes improving our energy efficiency and generating more electricity from renewable sources – including wind turbines offshore and onshore, hydro, wave, tidal, and biomass-combined heat and power – as well as the use of carbon capture and storage technology.”
Meanwhile, the SNP is seeking full devolution of the Crown Estate to ensure Scotland benefits from the offshore renewable energy boom. The Crown Estate is responsible for about half of Scotland’s foreshore and the seabed out to a 12 nautical-mile limit.
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