This is the first in a series of posts that look at GB Wind Power, in particular at its ability to contribute to peak demand, which occurs in the early evening, reaching its highest values during winter cold spells on working days. This post shows estimates for how much wind power would be produced if the 2016/17 wind generators encounter the weather conditions of the winter of 2011/12. Of particular interest is the wind power produced on the coldest evenings, quantified via the increase in minimum reserve capacity relative to a hypothetical no-wind system.
Data at 30-minute intervals for demand and “Estimated Embedded Wind” in winter 2010/11 were downloaded from National Grid and used to estimate “Residual Consumption” in 2011/12, and embedded wind power at 2016/17 levels. “Residual Consumption” is the name given here to the sum of demand and embedded wind, and represents the consumption not met by other (non-wind) distributed generators. Metered wind power for 2016/17 was estimated by scaling up the measured metered wind power data for 2011/12 to the typical levels seen for metered wind in late 2016. Metered wind power data was downloaded from the gridwatch website ( http://www.gridwatch.templar.co.uk/download.php ). Embedded wind power was scaled-up according to its total capacities in 2011/12 and 2016/17. See the NATIONAL GRID DATA page of this blog for a discussion of the accuracy of these estimation techniques.
The figure below shows the daily peak “Residual Consumption” (in red) and the estimated 2016/17 wind powers, for the winter weather of 2011/12:
The figure above shows the expected characteristics of GB wind power in winter 2016/17: it will be intermittent, it will be small compared with winter peak demands, and on some days it will almost vanish at the time of peak demand. To see the amount of wind power at the times of highest peak demand the data are plotted again in the figure below, with an arbitrary offset of 61 GW applied to the demand data. The 61 GW offset is indicative of how much dispatchable power was needed in 2011/12 to meet peak demand. The figure also shows the mean temperature of the Central England Temperature (HadCET) series:
The figure above shows that there was a mild and windy period in December/January, and a cold spell in February. The coldest days of February fell at weekends, but nevertheless there was a day of high peak consumption. To show more clearly the contribution of wind power to peak demand the following figure shows “Reserve Capacity”, for the arbitrary (though not unrealistic) choice of 61 GB of dispatchable supply, with and without the contribution of wind power:
The figure above shows that wind power at 2016/17 levels would provide an extra 1.9 GW of reserve capacity for this weather, at its working day sampling in 2011/12 . To assess the robustness of this wind power contribution to time shifts the following figure shows the half-hourly weather conditions measured at Cambridge for the entire cold period. We need to assess whether or not there were any potential high-consumption/low-wind days that might reduce the extra reserve capacity if they fall on working days.
The temperature/wind/consumption data shown above is repeated below, showing only January/February:
The two figures above show that the cold spell was quite poorly sampled (in terms of peak consumption), with only the cold day of 8th February falling on a working day. The cold weekend day of 4th February was quite windy, but not so the 11th February, which may have reduced the reserve capacity if it had fallen on a working day rather than on a Saturday.
Cold Weather Summary
The UK Met Office produced the following summary for 1st to 12th February 2012 for England ( http://www.metoffice.gov.uk/climate/uk/summaries/2012/february ):
1st to 3rd: A very cold easterly airstream resulted in daytime temperatures rising no higher than 3 to 4 °C in most areas, with the west generally brightest. By the 3rd, lighter winds allowed the cold to intensify, with -12.4 °C recorded at South Newington (Oxfordshire) overnight on 3rd/4th.
4th to 6th: During the weekend of 4th/5th, a band of rain, sleet and snow moved eastwards. Early on 4th, parts of the north-west saw freezing rain, with some glazed surfaces forming for a time before milder air turned the wintry mix to rain in western parts. Further east, many areas had their first significant snowfall of the winter, with 5 to 10 cm lying quite widely in central and eastern parts. The snow eventually cleared eastwards on 5th, with daytime temperatures staying around 0 °C in eastern counties.
7th to 12th: Cold continental air dominated conditions in the east, with lying snow helping to maintain the low temperatures. Further west it was often cloudier and much milder, with fronts becoming slow-moving, bringing significant ice at times on the boundary between the mild and cold conditions
The light winds of this cold spell are confirmed by the small number of isobars crossing GB on this synoptic chart for 3rd February 2012:
and in these ones from 10/11th February 2012 respectively:
Electricity Summary for winter 2011/12
The prolonged cold spell in February 2012 provides a key test case for the GB electricity system in future winters. Some days of very high peak consumption coincided with relatively light winds.