Multi-Year Hydro–PV Complementarity at the Belo Monte–Pimental Hydropower Complex

This paper evaluates the multi-year, multi-scale hydro–photovoltaic (PV) complementarity of the Belo Monte–Pimental run-of-river hydropower complex in the Brazilian Amazon and its implications for renewable-resource diversification and electricity planning. Official hourly hydropower-generation records from the Brazilian National System Operator were combined with physically modeled PV generation over 2021–2025, comprising 43,824 synchronized hourly observations. The raw-hourly hydro–PV association was weak (Pearson r=−0.119; Spearman ρ=−0.100), whereas substantially stronger inverse associations were observed for the mean intraday (r=−0.541; ρ=−0.560) and seasonal profiles (r=−0.580; ρ=−0.650). Seasonal correlations remained negative in all five analyzed years, while intraday association varied substantially among years. Capacity-equivalent scenarios from 1.1 to 1000 MWp showed progressively greater portfolio effects. At 1000 MWp, PV generation corresponded to 18.68% of the five-year mean dry-season hydropower energy, reduced the hourly portfolio coefficient of variation by 4.71%, and increased the daytime fifth-percentile generation by 191.2 MW. Under the sample-relative classification adopted for 2021–2025, 2024 was identified as the low-generation year. Its June–November hydropower generation was 1679.3 GWh below the five-year dry-season mean. Under the adopted PV model, this deficit corresponds to a seasonal energy-equivalent capacity of approximately 2327 MWp, while the 1000 MWp scenario would provide energy equivalent to about 43% of the observed deficit. The results characterize persistent seasonal diversification within the 2021–2025 observation window and capacity-dependent portfolio effects rather than hour-by-hour balancing, firm capacity, or coordinated hydro–PV dispatch.