This is the fifth 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. 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. In addition, estimated embedded wind power data was downloaded from National Grid (see the NATIONAL GRID DATA page of this blog for details) and plotted in order to help to understand the daily variation of peak demand.
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 winter 2015/16:
The red demand curve in the figure above shows periodic dips at weekends, more substantial dips on Christmas and New Years days, and moderate peak demands during a cold spell in January. The blue curve shows the intermittency of GB wind power, its small size relative to winter peak demand in 2015/16, and the fact that it almost vanished at several times of peak demand, though less often than average due to the sustained westerly winds in December and early January.
To show more clearly the contribution of wind power on the days of highest peak demand the data are shown again in the figure below, with an arbitrary offset of 54 GW added to the wind power. The 54 GW offset is indicative of how much dispatchable power was necessary to meet peak demand at that time. The figure also shows the NG-estimated embedded wind power at times of peak demand, and the sum of peak demand and embedded wind power, labelled as “consumption” (the intrinsic demand of consumers, some of which is met locally by embedded wind power):
The single cold (relatively high demand) spell in this period is evident on the figure above, starting in the middle of January. Some of the large (around 3 GW) jump in demand at this time was the result of a deep lull in embedded wind power, the “consumption” curve showing a lower jump. The mid-January cold spell has the following summary for England (indicating the low evening temperatures) and synoptic chart (indicating the light winds) from the UK Met Office:
“A” (15th to 21st January): “It was cold and bright on the 15th with scattered showers, these wintry on high ground and mostly in the west. After a dry, sunny and frosty start on the 16th, with a minimum of -5.7 °C at Benson (Oxfordshire), an area of rain, sleet and snow spread south-east during the afternoon. The 17th was cloudy with patchy light rain and temperatures near average. Patchy rain persisted in the north-east on the 18th but cleared the south-west. It was dry with a widespread frost on the 19th, sunny in the south, but cloudier in the north. It was cold, dry and sunny for most areas on the 20th, with -8.8 °C recorded at Benson and 7.8 hours of sunshine at Hastings (East Sussex). After another cold sunny start over central and eastern parts on the 21st, it turned cloudier, with patchy rain in the south-west and north.” The widespread light winds revealed by the wind power plot are confirmed by the following sample synoptic chart for 19th January 2016:
The following half-hourly data measured at Cambridge indicates that this was a relatively mild and short cold spell, and also confirms the light winds on the coldest days:
The following figure shows the same demand data as above, but with FOUR times the amount of metered wind power that was produced in this period:
The most problematic characteristic of the wind power produced during the cold spell in mid-January is that it is still very low, despite a fourfold increase, and there is considerable variability, especially in February.
The single week of relatively high peak demands (historically not very high, but higher than other weeks of winter 2015/16) had days of very low wind speeds at the times of peak demand. Later posts will combine the conclusions for each separate year into an overall conclusion on the reliance that can be placed on UK wind power at the times of highest peak demand.