1. A 33 yr climatology of extreme wind power generation events in Great Britain EMS Annual Meeting & ECAM (2013) Dirk Cannon a, David Brayshaw a, John Methven a, Phil Coker b, David Lenaghan c, Andrew Richards c, David Mills c, David Bunney c d.j.cannon@reading.ac.uk a Department of Meteorology, University of Reading, UK b School of Construction Management and Engineering, University of Reading, UK c National Grid, Wokingham, Berkshire, RG41 5BN, UK

2. Motivation Needs of transmission system operators (TSOs) to understand the frequency and severity of extreme wind power generation events

3. Motivation Persistent wind power generation

4. Needs of transmission system operators (TSOs) to understand the frequency and severity of extreme wind power generation events Motivation Rapid changes in wind power generation

5. Wind speed record from reanalysis data (MERRA, Rienecker et. al., 2011. J. Clim. 24, 3624–3648 ) Long time series (1980–2012) Consistent assimilation of observations Gridded data (can be used with any wind farm distribution) Reproduces majority of observed variability in 10 m wind speed on – spatial scales > 200–300 km, – time scales > 3–6 hours Methodology Methodology | 33 yr climatology | Summary and future work

6. 1. Wind farm distribution as of September, 2012; bi-linearly interpolated 2. Log-height extrapolation to turbine hub height 3. Transformation to Load Factor (LF) using idealised power curve Conversion to power Methodology | 33 yr climatology | Summary and future work

7. GB-aggregated over 215 wind farms: LF Note: MERRA-derived LF assumes constant wind farm distribution, whereas the real distribution constantly evolves Comparisons with NG data Methodology | 33 yr climatology | Summary and future work r = 0.96

8. Comparisons with NG data Methodology | 33 yr climatology | Summary and future work r = 0.73 r = 0.91

9. Persistent low wind How often do persistent low wind power generation events occur in an average year? Methodology | 33 yr climatology | Summary and future work

10. Persistent high wind How often do persistent high wind power generation events occur in an average year? Methodology | 33 yr climatology | Summary and future work

11. Rapid changes For how many hours in an average year is there a subsequent rapid change in wind power generation? Methodology | 33 yr climatology | Summary and future work

12. Inter-annual variability E.g., LF ≤ 6.3 % for persistence time ≥ 24 hr: Mean: 10 yr -1 Range: 2-18 yr -1 Methodology | 33 yr climatology | Summary and future work

13. Seasonal variability E.g., LF ≤ 2.2 % for persistence time ≥ 12 hr: Mean: 0.5 /season Range: 0.15 /winter 1.4 /summer Methodology | 33 yr climatology | Summary and future work

14. Summary Estimated the frequency and severity of extreme wind power generation events in Great Britain over the last 33 yr. Considered three extremes: 1)Persistent low wind power generation 2)Persistent high wind power generation 3)Rapid changes in wind power generation Return periods show large variations from year-to-year and season-to-season Quantitative results sensitive to power curve (not shown) Methodology | 33 yr climatology | Summary and future work

15. Future work Predictability of extreme wind power events GB-wide scales – On time scale of hours to days – Statistical and case study analysis Regional scales – Downscale to km-scale – Investigate extreme generation events & large forecast errors d.j.cannon@reading.ac.uk Methodology | 33 yr climatology | Summary and future work

16. Predictability of extreme wind power events GB-wide scales – On time scale of hours to days – Statistical and case study analysis Regional scales – Downscale to km-scale – Investigate extreme generation events & large forecast errors d.j.cannon@reading.ac.uk