Power On - Wind

| 1st November 2007
The UK has been described as the ‘Saudi Arabia’ of wind, with some 50 TWh of onshore and at least 450 TWh of offshore power available every year, well in excess of our current electricity demand.

But wind has recently become the whipping boy of environmental technologies. Turbines are branded as ugly and ineffective, generating energy for only a small proportion of the time, and requiring substantial fossil fuel capacity to provide backup for when the wind doesn’t blow.

The biggest bugbear is known as ‘capacity factor’. This is the percentage figure applied to all power generation technologies, which indicates for what proportion of the year they operate at full, specified output. Onshore wind farms are generally regarded as having a capacity factor somewhere between 30 and 40 per cent, with offshore farms closer to 45 per cent.

Poor reporting in the media has led to this capacity factor figure being interpreted as the amount of time for which wind turbines generate electricity, leading to the popular myth that you only get wind energy for one third of the time. This is quite wrong. Most well-sited wind turbines generate power for 80–85 per cent of the year, but not necessarily at their peak capacity, owing to all sorts of reasons, including weather, maintenance work or mechanical restrictions.

It is worth noting that while the capacity factor for wind farms is between 30 and 45 per cent, the capacity factor for hydro-electric plants is around 37 per cent, for gas power plants 60 per cent, coal plants 62 per cent and the historical average capacity for the UK’s ‘always on’ nuclear fleet only works out at 62 per cent.

Wind energy has huge potential, particularly if backed by energy storage technologies such as hydrogen or tidal lagoons. It remains only for the technology to be deployed sensitively, and in partnership with local communities or businesses.

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This article first appeared in the Ecologist November 2007

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