Assessing Shortfall Risk of UK power systems using shifts in winter weather Conditions

Extreme weather during winters have a significant impact on the security of supplies for power systems over the UK. Extremely low temperatures combined with low to moderate wind periods increase the net demand relative to the available renewable energy supply in the system potentially leading to disruptions and power cuts. This work introduces a novel way of shifting weather over time in a standard risk assessment framework to make maximum use of limited data on weather extremes in order to determine their worst-case possible impact if the demand is not moderated for example, by the Christmas or weekends during winters. The proposed method involves first mapping the historical weather from ERA-5 to electricity demand and generation time series using a regression model.  The historical data is then scaled to different scenarios of demand and generation for current day and future. Once the rescaled series of demand and generation are obtained, a shifting operation in weather is performed forward/backward in time to obtain the final synthetic demand and generation series that can be used to assess risk of supply shortages. There is interesting application of both meteorology and power system engineering in this work and by shifting weather over time, more extreme weather days which fall on weekends or the Christmas period can be redistributed to peak demand periods (during weekdays) giving a more comprehensive perspective on how weather links to shortfall risks. Our analysis shows that for instance, during the extremely negative NAO winter of 2010-11, the effect of extremely low temperature and low-to-moderate wind conditions on demand and supply could have been worse even if the weather patterns had shifted slightly just by a few days. If a three day forward shift in weather patterns was observed, the shortfall risks increase from 1.9 to 2.9 days/winter as few colder days from the Christmas weeks are brought to the beginning of January for present day conditions. When the same shift in weather conditions are assumed in a higher weather sensitive scenario with increase in temperature sensitivity of demand from -0.6 GW/°C to -1.0 GW/°C and, increase in installed wind generation capacity from 15 GW each to 30 GW onshore and 20 GW offshore respectively in the future, the risk levels fall to 1.1 days/winter. This highlights how scaling up the wind generation capacity over the coming years will reduce reliance on conventional sources of energy and ensure a stable electricity supply, even under extreme conditions, while addressing the challenge of growing demand driven by increase in electrification in the future.