It is commonly known that 2015 was a great year for wind asset owners in Europe, with yields exceeding average values. High expectations were set for the years to come, however unfortunately, 2016 did not follow the same trend.
The Wind Index, as calculated by 3E, is a useful tool to show the wind potential of a certain period with respect to the long-term. The analysis carried out by 3E is based on the MERRA2 reanalysis dataset from NASA and focuses on the entire year 2016. The results demonstrate that the past year was among the worst wind years of the last decade in Western Europe.
3E’s approach to wind index
3E has two distinct approaches to assessing the wind index: one way is what we call the “Cumulative” Wind Index, comparing the wind performance of a certain month with respect to the average monthly wind performance of the past 10 or 20 years (the reference period). This method is typically used for long term extrapolation based on the Wind Index.
The “Short Term” Wind Index shows the wind performance of a given month with respect to the average performance of the same month for the past 10 or 20 years. The main difference between the 2 approaches is that the second one eliminates the effects of seasonality, and is used to look at the performance of a specific month.
Bad wind year for Belgium, even worse for France
In the present analysis, the “Cumulative” Wind Index for Belgium was based on 17 reference points spread over the country. Results demonstrate that the wind index for 2016 represents 93% of the average over the past 10 years (2006-2015). This implies that the energy production potential of wind in Belgium during 2016 was 7% lower compared to the previous 10 year reference period. Over the last decade, only 2010 did worse.
In the following graph, the 100 line (Benchmark) represents the average wind potential of the considered reference period.
The “Cumulative” Wind Index for France was based on several high potential points spread over the country. The figures for France show an even stronger decrease for 2016, with an average wind index of 91.7% for the considered points. This demonstrates that on average the drop in wind potential during 2016 is higher in France than in Belgium. Here, 3E’s analysis shows that 2016 was the worst wind year out of the last 10 years.
Furthermore, significant regional variability is observed within the investigated areas, with a difference of 8.5 percent between the two extremes.
Even though it started good…
A “Short term” Wind Index analysis for the same period and data points, shows that the first 3-4 months of 2016 have higher wind speeds compared to values of long term average of those months. In certain regions, there are even months with Wind Indices exceeding 150%. However, for the remainder of the year, every month was far below 100%.
How does this translate in production values?
A decrease in wind index values also corresponds to a decrease of the wind farm production for the considered period with respect to the expected long-term average. However, such variation over time is a very well-known phenomenon and can be modeled relatively easily. 3E’s uncertainty analysis, which is part of a standard P90 calculation, typically accounts for this concept through the future wind variability. Any P90 figure would therefore sufficiently cover for these lower wind periods.