Can we rely on the wind?

Wind energy is often criticised for being unreliable. Critics claim that wind energy can never replace existing power stations, or remove the need for new power stations to be built, because the wind cannot be relied upon. In technical terms this argument boils down to the question; 'can wind energy be regarded as having a capacity credit?'

Wind energy can be relied upon, even though the wind is not available 100% of the time. Wind turbines generate electricity for 70-85% of the time, but not always at full output. Most wind turbines start generating power at wind speeds of around 3 or 4 m/s (when the output is a few kilowatts), generate maximum ("rated") power at around 15 m/s and shut down to prevent storm damage at 25 m/s or above. The proportion of time that wind turbine is generating between these wind speeds depends on the average wind speed at the site. Most sites where wind turbines are installed in the UK have wind speeds in the range 7.5 - 9 m/s and so generate for 70-85% of the time.

 

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