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.
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.