18 November 2019
An increase in wind speed in recent years is good news for renewable energy production. Average global wind speed had been dropping since 1978, but this trend has reversed over the past decade.
Zhenzhong Zeng at Princeton University and his colleagues analysed data on wind speed recorded at ground weather stations across North America, Europe and Asia between 1978 and 2017.
The researchers found that from 2010 to 2017, average global wind speed over land increased by 17 per cent – from 3.13 to 3.30 metres per second. Before this, from 1978 to 2010, wind speed had been falling by 0.08 metres per second – or two per cent – every decade. The reversal came as a surprise, says Zeng.
Wind speed was thought to be declining because of increasing urbanisation resulting in more barriers, such as buildings, that slow down moving air. Why average global wind speed has been increasing since 2010, despite no reduction in urban development, isn’t known, says Zeng.
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Other factors have been blamed for the longer-term slow down and these could mean the recent speed up is a blip. Wind in mid-latitude regions, where most turbines are located, arises due to the large temperature difference between the equator and the poles. This temperature difference is getting smaller because of global warming, which is happening more quickly at the poles, and so the trend of decreasing wind speeds is likely to return, says Kristopher Karnauskas at the University of Colorado Boulder, who wasn’t involved in the study.
Karnauskas says that, while there has been a longer-term trend for decreasing wind speed since 1978, it is still important to pay attention to short-term fluctuations. “The 2010 turning point – that’s an indication that these short-term fluctuations are enough to overpower the long-term trend,” says Karnauskas.
Knowing whether wind speed is going up or down will allow us to predict how much wind energy we can expect to have access to in future, Zeng says. It has been predicted that 7 per cent of global electricity demand will be met using wind energy by 2024. To produce energy efficiently, wind turbines need a wind speed of at least 3 metres per second.
Journal reference: Nature Climate Change, DOI: 10.1038/s41558-019-0622-6
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