Wind power variability during the passage of cold fronts across South Africa

Abstract

Wind is a naturally variable resource that fluctuates across timescales and, by the same token, the electricity generated by wind also fluctuates across timescales. At longer timescales, i.e., hours to days, synoptic-scale weather systems, notably cold fronts during South African winter months, are important instigators of strong wind conditions and variability in the wind resource. The variability of wind power production from aggregates of geographically disperse turbines for the passage of individual cold fronts over South Africa was simulated in this study. When considering wind power variability caused by synoptic-scale weather patterns, specifically cold fronts, the timescale at which analysis is conducted was found to be of great importance, as relatively small mean absolute power ramps at a ten-minute temporal resolution, order of 2-4% of simulated capacity, can result in large variations of total wind power production (at the order of 32–93% of simulated capacity) over a period of three to four days as a cold front passes. It was found that when the aggregate consists of a larger and more geographically dispersed set of turbines, as opposed to a smaller set of turbines specifically located within cold-front dominated high wind areas, variability and the mean absolute ramp rates decrease (or gets ‘smoothed’) across the timescales considered. It was finally shown that the majority of large simulated wind power ramp events observed during the winter months, especially at longer timescales, are caused by the passage of cold fronts.

Complexity and Persistence of Price Time Series of the European Electricity Spot Market

“…Fluctuations in renewable energy production on different time scales are strongly influenced by weather regimes and systems, like e.g., blocking regimes, low pressure systems, and the passage of fronts [78][79][80]. Inherently, so are electricity prices because of the merit-order effect.…”

Simulation and detection of wind power ramps and identification of their causative atmospheric circulation patterns

“…Electricity generated by wind turbines is a function of wind speed, and wind speed is variable across time scales. At longer timescales of hours to days, wind resource variability is driven by atmospheric circulation patterns and resultant synoptic-scale weather systems (Dalton et al, 2019;Kiviluoma et al, 2016). Large fluctuations in wind power within a defined timeframe are known as wind power ramps.…”

“…In a review article on the state of wind power ramp forecasting , it was found that linking ramp events to the underlying large-scale causative meteorological phenomena is important to the development or improvement of ramp forecasting frameworks. Indeed, various studies have successfully linked ramp events or wind power variability to underlying meteorological factors (Brayshaw et al, 2011;Dalton et al, 2019;Gibson & Cullen, 2015;Kalverla et al, 2017). It was however noted by that the findings from such studies are difficult to generalize to other cases and regions, as these would naturally be subject to different meteorological factors, terrains and wind farm layouts.…”