A report in the Guardian today included a rather curious statement. Covering a speech by Labour Party leader Ed Milliband at Whitelee Wind Farm near Glasgow, Damian Carrington claimed the following:
The windfarm, which spreads out across low, heather-clad hills, currently has 140 turbines and will add another 75 turbines soon, giving it a capacity equivalent to more than half a nuclear power station (about 550MW).
Now, it is true that the capacity of most nuclear power plants is somewhere around 1000 MW, however one would expect that a journalist who regularly writes about energy would understand that 550 MW of wind was not equivalent to 550 MW of nuclear.
So, how much of a 1 GW nuclear power plant would 550 MW of wind be equivalent to? For a start the (“nameplate”) capacity of a plant is its maximum output, not its average output. Wind power, as everyone knows varies. The key issue here is capacity factor, the ratio of actual output against its “nameplate capacity.” The US for example has the world’s largest nuclear fleet and had an average capacity factor of 89% in 2011. (figures for other countries available here)
What about Whitelee Wind Farm? Based on this marketing leaflet for the extension of Whitelee, its current capacity factor is about 30%. So, instead of the wind farm’s capacity being the equivalent of half a nuclear power plant, as the Guardian claimed, it is the equivalent of less than a quarter.
None of this is anti-wind, it is simply pro-arithmetic.