Variable renewable generation, primarily from wind and solar, introduces new uncertainties in the operation of power systems. This paper describes and applies a method to quantify how wind power development will affect the use of short-term automatic reserves in the future South African power system. The study uses a scenario for wind power development in South Africa, based on information from the South African transmission system operator (Eskom) and the Department of Energy. The scenario foresees 5% wind power penetration by 2025. Time series for wind power production and forecasts are simulated, and the duration curves for wind power ramp rates and wind power forecast errors are applied to assess the use of reserves due to wind power variability. The main finding is that the 5% wind power penetration in 2025 will increase the use of short-term automatic reserves by approximately 2%. Highlights • Simulations are validated against observations of 30 minutes ramp rates. • Absolute wind power ramp rates increase from 2014 to 2025. • Normalised wind power ramp rates decrease from 2014 to 2025. • Wind power will not impact the use of instantaneous reserves. • Wind power will increase use of regulating reserves with less than 3% in 2025.

Objectives To examine the effect of surgical approach on perioperative morbidity and mortality after partial nephrectomy. Materials and Methods Within the Nationwide Inpatient Sample, patients who underwent RAPN or LPN between October 2008 and December 2009 were identified. Propensity-based matching was performed to adjust for potential baseline differences between the two groups. The rates of intraoperative and postoperative complications, blood transfusions, prolonged length of stay, and in-hospital mortality, stratified according to RAPN vs. LPN, were compared. Results Overall, 851 (72.5%) patients underwent RAPN and 323 (27.5%) underwent LPN. For RAPN and LPN respectively, the following rates were recorded in the propensity-score matched cohort: blood transfusions, 4.5 vs. 6.8% (p = 0.223); intraoperative complications, 5.2 vs. 2.6% (p = 0.096); postoperative complications, 10.6 vs. 13.5% (p = 0.268); prolonged length of stay, 6.8 vs. 9.4% (p = 0.238); in-hospital mortality, 0.0 vs. 0.0%. Conclusions RAPN has supplanted LPN as the predominant minimally invasive surgical approach for renal masses. Perioperative outcomes after RAPN and LPN are comparable. Interpretation of these findings needs to take into account the lack of adjustment for case complexity and surgical expertise.