This is the second in a series of posts that look at UK 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. Of particular interest is the wind power produced on the coldest evenings.
Data at 5-minute intervals for demand and metered wind power were downloaded from the gridwatch website ( http://www.gridwatch.templar.co.uk/download.php ) and plotted so as to reveal its essential characteristics.
The figure below shows the daily peak demand (in red) and metered wind power (in blue) at the times of the daily peak demand, for 2012/13:
The red demand curve in the figure above shows periodic dips at weekends, more substantial dips on Christmas and New Years days, and substantial peak demands during cold spells in December, January and March. The blue curve shows the intermittency of UK wind power, its small size in 2012/13, and the fact that it almost vanishes at many times of peak demand.
To show the contribution of wind power on the days of highest peak demand the data are plotted again in the figure below, with an arbitrary offset of 57 GW added to the wind power. The 57 GW offset is indicative of how much dispatchable power was necessary to meet peak demand at that time.
Four cold spells with high peak demand are marked as “A”, “B”, “C” and “D” in the figure above. UK Met Office weather summaries and sample synoptic charts are as follows:
“A” (10th-13th December 2012): “Pressure built, and there were then a few days of quiet anticyclonic weather, allowing the first really severe frosts of the season. 10th was bright and sunny for most, with the exception of light wintry showers in the east. Overnight fog was often slow to clear during the day and caused some travel problems.” Light winds are confirmed by the absence of isobars in the following synoptic chart for 11th December 2012:
“B” (15/16th January 2013): “Eastern coastal areas had snow showers on 15th, and away from the far south-west temperatures were below average. After a frosty night on which Marham (Norfolk) recorded -13.1 °C, 16th was a quieter day, remaining cold with many areas away from the far south-west remaining below freezing all day.” Light winds are confirmed by the absence of isobars crossing the UK in the following synoptic chart for 16th January 2013:
“C” (21st-25th January): “The 21st saw a widespread frost and a cold but bright day, with northern and north-eastern areas getting some snow. After another cold start on 22nd, when Buntingford (Hertfordshire) fell to -13.6 °C, snow in the north-east gradually died out, by which time Redesdale (Northumberland) had a depth of 28cm. Later that day another band of rain and snow spread to the south and south-west, which lasted for much of 23rd over southern areas and the Midlands. The 24th was drier and brighter, but remained cold after a frosty start. On 25th an area of rain for coastal areas, but snow for many other areas, spread from the west during the afternoon, and parts of the north-west received 10 cm of fresh snow.” Light winds are confirmed from the wide spacing of isobars over the UK shown on the following synoptic chart for 24th January 2013:
“D” (11/12th March): “The 10th was much colder than of late, with a strong east wind and snow showers for eastern areas. It remained cold on 11th with strong north-east winds and snow showers, and an area of more persistent rain and snow for the Channel Islands where Jersey Airport recorded 5 cm snow-depth. Still cold, with scattered coastal snow showers on 12th, and an area of snow over the south-east and the Channel Islands where Guernsey recorded 14 cm snow-depth. After a frosty start, 13th was another cold day with frequent snow showers. The 14th began with temperatures dipping to -8.1 °C at Benson (Oxfordshire) and -8.2 °C at Shap (Cumbria), but during the day there was rain for the north-west and showers in the south-east.” The strong NE winds are confirmed from the high pressure gradient shown on the following synoptic chart from 12th March 2013:
The 3 highest demand cold spells in winter 2012/13 (“A”, “B” and “C”) were associated with light winds, and wind power contributed little to meeting demand. There was a cold spell in March with strong North Easterly winds, with wind power making a significant contribution to meeting demand, but the peak demand was significantly lower than in the 3 coldest spells.
Other posts in this series look at other years, culminating in an overall conclusion (TBD) on the reliance of wind power during UK winter peak demand periods.