Some of Britain’s biggest wind farms are at times producing only enough electricity to make a few cups of tea, according to official industry figures.
Data released by one of the largest green energy companies shows wind farms producing enough electricity only to boil two to three kettles at a time.
At one stage last week, three big wind farms even took electricity out of the National Grid – to run basic power supplies on site – rather than actually supplying electricity to households.
The wind farms’ owner said that in still conditions electricty “import” can occur for a few hours until the wind picks up. Such a phenomenon is known in the industry as “parasitic consumption”.
The data reveals just how much electricity is being generated by each wind farm at a given moment.
It is published by RWE npower renewables, a subsidiary of a German energy company operating 27 wind farms across England, Scotland and Wales,
The figures show just how little electricity giant turbines produce at certain times bolstering claims by critics that wind turbines cannot be relied upon to provide a constant source of electricity.
The Telegraph examined a snapshot of RWE’s own figures on Thursday afternoon last week. One wind farm Trysglwyn, which is in Anglesey in Wales, was producing a total of 6 kilowatts (KW) – just enough to boil two kettles each with 3KW of power.
The wind farm has 14 turbines and a theoretical capacity of 5.6 megawatts (MW). In other words, the wind farm was producing just 0.001 per cent of its maximum capacity.
Little Cheyne Court wind farm, which consists of 26 turbines each of them 377ft high, was producing 129KW of electricity last Thursday afternoon.
The wind farm, which was hugely controversial when it was built at a cost of £50 million on the site of Romney Marsh in Kent, is the largest in the south east of England.
Its supply last Thursday was equivalent to the boiling of just 43 kettles – or 0.002 per cent of its maximum capacity of 59.8MW.
At the same time in the very north of Scotland, near Wick, Bilbster wind farm was producing 268KW of electricity, the equivalent of boiling 89 kettles. The wind farm consists of three turbines each 295ft high.
According to RWE’s own data, three wind farms on Thursday afternoon appeared to be taking electricity from the National Grid rather than supplying it.
The eight turbines at Knabs Ridge, which is close to Harrogate in Yorkshire, used up 86KW of electricity while Lambrigg wind farm’s five turbines in Cumbria took 10KW from the grid.
Llyn Alaw wind farm, which is in Anglesey, and consists of 34 turbines also produced a negative output, according to RWE’s own data, of minus 80KW.
RWE is thought to be the only one of the major electricity generating companies to publish such detailed, instantaneous information on the power supplied by its wind farms.
Opponents of wind turbines, who claim they are also costly to run and unsightly, say RWE’s figures show just how unreliable wind energy is.
While the snapshot analysed by the Telegraph shows how little electricity was produced by some wind farms on still, summer days, there have been other times in the past month when wind farm owners have been paid by the National Grid to shut down in order not to over load the electricity supply system.
Such payments – known as constraint payments – have reached £7.5 million for the first three weeks of August.
In other words, claim critics, there are times when turbines produce too much electricity and moments when they do not produce enough.
The Government has been keen to promote wind energy in its attempt to meet a European Union-wide target of providing 15 per cent of energy needs from renewable energy by 2020. The Labour government introduced a consumer subsidy, added on to electricity bills, to encourage the construction of wind farms.
That subsidy is predicted to rise to £6 billion by 2020.
John Constable, director of Renewable Energy Foundation, a think tank which has been critical of wind farms, said: “Professional analysts have long known that fluctuating wind turbine output is poorly correlated with demand, but RWE’s new website is a very valuable addition to the data available to the general public, and will encourage informed debate about the relative potential for different renewable technologies.
“The truth will be painful for some, but the facts have to be faced sooner or later.”
Dr Constable added: “The uncontrollably variable output of wind power already imposes significant grid and system management costs on the consumer, costs which are set to grow dramatically; we need to ask ourselves whether the EU renewables targets for 2020 are really affordable.”
RWE said the company through wind farms and hydroelectric schemes had the capacity to produce enough renewable energy for 800,000 households. RWE npower renewables is the UK subsidiary of RWE Innogy and one of the UK’s leading renewable energy developers and operators.
A spokeswoman said: “Low wind speeds were the primary cause of the figures observed at the sites in question yesterday. For a few hours these sites had no generation or a very small amount of import.
“In very low wind conditions import can occur to power wind farm control systems and keep turbines ready to respond when the wind picks up. These are very small amounts of consumption.
“August is generally a low wind month and also one of the lower months for consumption.
“Wind turbines generate clean energy in the region of 80-85% of the time from fuel delivered straight to the point of generation without the impacts from extraction, transportation or supply security challenges. As such wind energy is inherently efficient.”
RenewableUK, the trade body representing the wind industry, said the UK possessed “the best wind resource in Europe”.
Maf Smith, its deputy chief executive, said: “You need to look at the year as a whole – the latest Government figures show that in 2012, more than 11 per cent of the UK’s electricity came from renewable sources, with wind providing the lion’s share.
“We hit a new record in March when we generated enough electricity from wind at one point to power four out of 10 British homes.
“So while our critics may choose to pick out individual examples of periods when it was less windy, we prefer to look at the bigger picture as that’s far more representative overall.”
Wind farms: how they performed
The electricity produced by RWE wind farms at approximately 5pm on Thursday August 22:
Bilbster, Caithness, 268KW
Knabs Ridge, North Yorkshire, -86KW
Lambrigg, Cumbria, -10KW
Little Cheyne Court, Kent, 129KW
Llyn Alaw, Anglesey, -80KW
Tow Law, County Durham, 30KW
Trysglwyn, Anglesey, 6KW
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