Fifteen Eighty Four

Academic perspectives from Cambridge University Press


How reliable is wind energy?

Colin G. Anderson

Using wind energy to generate electricity has been a big topic in the climate change discussion for many years. But can we rely on renewables like wind to take up the slack as we begin to phase out fossil fuels? With the promises and ambitions of COP26, this point is increasingly important. One of our authors, Colin Anderson, the author of Wind Turbines: Theory and Practice, explores the debate.

In energy policy debates we sometimes hear the complaint that because wind energy is intermittent, it can’t be ‘reliable’. Is this a fair criticism? It all depends on your timescale. Taking a short term view, it is true that the amount of energy generated by a wind turbine on a particular day can’t be predicted far ahead with accuracy. Taking a longer term view, however, we know that as long as the sun shines and the earth turns, there will be wind energy generated – and on an annual basis, it is more predictable than you may realize.

The graph below shows the annual output of a 3-turbine wind farm in Aberdeenshire, North East Scotland, over the 12 years since it was commissioned in 2007. There is some year-to-year variation, but in no year did the output fall below 90% of the long-term average. Once that wind farm was built, the owners knew more or less how much energy they would get each year; there wasn’t a ‘bad’ year.

Annual output of Hill of Easterton wind farm, Aberdeenshire
(Source: ROC register)

We can compare this with more conventional generating plant. Nuclear power is widely regarded as a key source of baseload electricity, and the graph below shows the annual output of Torness, Scotland’s largest nuclear power station, over the same 12-year period as above (data from IAEA PRIS). According to this, Torness had more ‘bad’ years than the wind farm, and in the worst case output dropped below 60% of the long term average.

Annual output of Torness-1 (Source: IAEA PRIS)

This comparison doesn’t address the issue of daily or seasonal variability of wind energy, and the challenge for the future is to smooth out the short-term variation in wind output by a variety of means including energy storage, grid management, and integration with other renewable power sources. It does show, however, that the wind resource is extremely reliable – guaranteed, even – on an annual basis.

Follow this link to find out more about Colin’s book on wind turbines:

About The Author

Colin G. Anderson

Colin G. Anderson is a consulting engineer specialising in renewable energy technology and an adjunct lecturer at the School of Engineering, University of Edinburgh, where he teach...

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