Frequency, duration, severity of energy drought and its propagation in hydro-wind-photovoltaic complementary systems

Abstract

Analyzing low-renewable-output events, termed “energy droughts” is crucial for renewable energy systems. However, due to the challenges in hydropower regulation and complex spatiotemporal correlations among resources, the assessment and contributions of various resources to energy droughts in hydro-wind-photovoltaic (PV) energy systems (HWPSs) remain unexplored. To address these issues, this study evaluated energy droughts and compound resource droughts rather than single-resource in HWPSs, exploring the propagation. Assessments of frequency, duration, and severity relied on weather-to-resource conversion models and total power obtained through complementary operation. Estimating propagation probability from resource to energy droughts was achieved via the C-vine copula, quantifying resource contributions to drought propagation. Results of a case study in the Yalong River Basin indicated that (1) short-lived compound resource droughts have been increasingly frequent recently, peaking during winter or summer. After incorporating hydro energy resources, the severity and annual average occurrence of compound droughts decreased (from 18.56 to 5.24 events/year). (2) Complementary operation effectively reduced the probability of drought propagation. (3) Hydro and PV energy resources were pivotal contributors to drought propagation, contributing 49.1 % and 40.1 % when representing 53.4 % and 22.5 % of the total system capacity, respectively. Therefore, the study offers valuable insights into energy drought warnings and risk mitigation.