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UK windiness 2017: First semester lower than long-term expectations – what are the impacts for you?

Monitoring, recording and interpreting wind speed trends can be extremely valuable to wind farm investors, owners and operators, enabling project performance to be assessed and evaluated. But what do the 2017 first semester results mean for you?

2017 wind speed trends

In our last blog, we highlighted how 2016 provided lower than average wind speeds. Using our UK Wind Index, wind speed trends across the UK for the first six months of 2017 have been captured and are presented in the below figures. For reference, the monthly index for 2016 is also shown to enable comparisons between both years.

The data shows that February and March almost matched the long-term wind speed trends for those months, while April and May both recorded below average wind speeds. However, January and June both recorded extraordinary wind speeds compared to long-term expectations. January 2017 was 21% below the long-term average for that month – it was the least windy January since 2010. Wind speeds in January were 8% below the overall long-term average. This is unusual as January is typically the windiest month of the year according to long-term data. Only May has seen lower wind speeds than January in the first half of this year. Conversely, we experienced the windiest June in 15 years, with the average wind speed 14% above the long-term average for June.

The six-month period has been 4% less windy than the long-term average for the first semester. These results are similar to the same period last year. As the second quarter of 2017 matched the long-term average for this period, the deficit over the full six-month period is mostly due to the low wind speeds observed in January.

If seasonal effects are not considered, the first semester of 2017 has been approximately 1% less windy than the long-term average of the entire UK Wind Index. This indicates that the average wind speed of the first semester of 2017 is reasonably representative of the expected long-term wind speed.

A full breakdown of the monthly and quarterly wind indices for 2017 is given in the tables below, along with the ‘windiness’ for each complete year in the index.

Reviewing the wind to establish results

How will this drop in mean wind speed impact owners, investors and developers?

Wind farm owners are likely to have seen lower production at their projects during the first six months of 2017, compared to the long-term average for this period. Using typical project wind speed to energy sensitivity ratios, production figures approximately 6-8% lower than the long-term average would be expected. This should be taken into consideration in reviews of the performance of a project. This approximately matches the same period last year, in which similar wind speed trends were observed.

Wind farm developers who have been conducting wind measurements during the first semester of 2017 can expect the average wind speed to be lower than the long-term average and this should be taken into consideration when adjusting measurements to be representative of a long-term period.

What does this mean for the remainder of 2017?

Will the wind speeds in 2017 continue to recover from the slow start to the year? Will they exceed the 20 year average wind speed record set in 1998? We will publish our full 2017 wind speed trends review in early 2018. Watch this space!

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