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UK windiness 2016: Wind sets a new UK generation record despite lower than average wind speeds

In December 2016, the UK wind industry set a new record by generating more than 10,000 MW of electricity for the first time and providing 23% of the UK’s electricity demand. We continue to see wind energy playing a pivotal role in the UK’s electricity mix, even in a year that saw wind speeds approximately 5.5% lower than the long-term average. In this blog, DNV GL’s Gemma Daron reviews 2016 UK wind speed trends and assesses the impact on your assets.

2016 wind speed trends

In our last blog, it had become apparent that the first six months of 2016 were 4% less windy than the long-term average for a first semester. Since then, although July to September were windier than long-term expectations, the second semester was 7% less windy than long-term expectations. This is largely driven by the October to December period, which was significantly less windy than the long-term trend. In fact, October 2016 was more than 20% below the long-term average for the month.

Overall, our UK Wind Index demonstrates that 2016 was 5.5% less windy than the long‑term average and it’s also been recorded as the second year with lowest wind speed in the 21-year index.

A full breakdown of the monthly and quarterly wind indices for 2016 is given in the tables below, along with the ‘windiness’ for each complete year in the index. For ease of referencing, the monthly index for 2015 is also shown.

Interpreting the data to establish an answer

But what does the significant drop in mean wind speed during 2016 represent for owners, investors and developers?

Wind farm owners can expect to have seen lower production at UK projects during 2016, compared to 2015, because of the reduced windiness. Using typical project wind speed to energy sensitivity ratios, it is noted that a 5.5% reduction in wind speed corresponds to a reduction of approximately 8% to 11% in terms of energy production. This should be taken into consideration during reviews of project performance.

Wind farm developers who have been conducting wind measurements during 2016 can also expect the average wind speed to be lower than the same period in 2015. This trend should be taken into consideration when adjusting measurements to be representative of a long-term period.

However, the observed 2016 deviation from the long-term mean wind speed is noted to fall within the expected range of wind speed inter-annual variability. Thus, whilst 2016 has been a low wind speed year, this event is expected to be covered by “industry standard” assumptions for future wind speed uncertainty, as modelled in energy production assessments.

But what impact does this have for future UK energy generation?

Will the wind speeds recover in 2017? Will wind energy generation continue to break records as more projects come online? We will publish our mid-year wind speed trend review in July 2017. Stay tuned for more!

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About the UK Wind Index

Monitoring and recording wind speed trends can be beneficial to assess project performance. But interpreting and truly understanding those trends are where the real value lies.

The UK Wind Index           

DNV GL maintains a UK Wind Index, which enables owners and investors to assess the performance of potential or operating projects. Likewise, the UK Wind Index is a robust tool for wind farm developers, empowering them to understand the ‘windiness’ of their wind monitoring campaigns compared to a long-term period.

The UK Wind Index is continually maintained with a wealth of monthly average wind speed data from over 60 Met Office stations geographically spread across the UK mainland. Our tool covers the long-term period, from January 1996 to the present day.

The UK Wind Index is normalised so that the average wind speed over the period January 1996 to the present day is 100%, for a period representing all complete years in the index. The windiness of any given period is expressed as a percentage of the long-term average wind speed. Thus, a value exceeding 100% indicates that a period was windier than the long-term average, whilst a value below 100% suggests that a period was less windy.

Seasonal effects

Wind speeds in the UK exhibit strong seasonality, with a tendency for higher wind speeds during the winter months and lower wind speeds during the summer months. As a result, we in DNV GL also derive a seasonally adjusted UK Wind Index, which has been corrected for seasonal bias.

To be more precise, the windiness of any given period is expressed as a percentage of the long-term average wind speed for that specific period. For example, the long-term windiness of the month of January is 116%. If a specific (individual) January has an index value of 105%, the seasonally adjusted value for that January would be 105%/116% = 91%. In this case, this January is less windy than the long‑term average for January, despite being windier than the long-term average of the index.

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