Análises numéricas e observacionais de geração hidrelétrica na bacia hidrográfica do rio São Francisco.

Abstract

Long-lasting droughts and torrential precipitation events are phenomena of increasing frequency and equally harmfull at short, medium or long range horizon. In severe drought periods the water for electriciy generation is limited. The irregular rainfall distribution interferes on the levels of the reservoirs. The scenario of water shortage that struck the country in the period from 2012 to 2016 reduced the water inflow to the reservoirs, and the energy generation by the hydroelectric power plants was considerably reduced. In this work precipitation anomalies in the São Francisco Hydrographic Basin and impacts of variations in IEN (inflow energies) and SEN (stored energies) in the Northeast subsystem were analyzed using the SPI (Standardized Precipitation Index) and the NEWAVE model used by ONS, the National Electric System Operator of Brazil, to provide support to the planning of the Brazilian hydrothermal system operation. The results indicate that the use of SPI represents an eficient method for monitoring meteorological and hydrological droughts impacts upon the hydrothermal electric energy production. The water inflow to the Sobradinho reservoir is strongly dependent on the High São Francisco precipitation regime. The simulations performed with the NEWAVE (Long and Medium Term Operation Planning Model for Interconnected Hydrotermal Systems) show that the model was successfull in indicating a tendency for a drop in the values of SEN in the drought period. The model gives priority to the hydroelectric over the thermal generation as the most adequate method to assure a minimum storage level in the reservoirs. The Northeast subsystem is mainly importer with exception of the water shortage period in which the eolic energy source predominates in the electric energy generation