Avaliação da variação da garantia física em função das mudanças no regime hidrológico da bacia e da motorização dos grupos geradores das pequenas centrais hidrelétricas

Abstract

In the national scenario, where the hydraulic source is predominant, the Physical Guarantee (PG) of a Hydroelectric Plant becomes a fundamental component to develop efficient and sustainable energy planning. PG concerns how much a source is capable of supplying assured or granted demand. One of the main factors that influence generation from this source is water availability. The present work evaluated the influence of hydrological variations on the amount of PG of Small Hydroelectric Plants (SHPs) in operation using the following criteria: consideration of fixed or variable losses and efficiencies (turbines, generators and adduction system); application of monthly or daily average flows; series extension as complete or last 15 years; inclusion or not of the central motorization. Three methodologies were used, one of them being the current method, from the Ministry of Mines and Energy (MME), the other the Variable Efficiencies Method and, finally, the Unit Electric Power Method, developed in this dissertation. It was possible to verify that the water availability of the samples has been lower in recent years, with some influence from water crises, and this factor is reflected in the PG, which in 100% of the SHPs was lower when the series was extended over the last 15 years. Of the SHPs evaluated, in 7 of them it was not possible to obtain a PG calculated above the PG granted by ANEEL and, in the 2 in which it was possible, only when the complete series was applied. Furthermore, the MME Method, which applies monthly average flows, resulted in the highest results in 100% of SHPs compared to the other 2 methods, which apply daily average flows. The Unitary Electrical Power Method, developed in this work, generally presented the lowest PG values. The dispersion of results was relatively high, with cases in which the standard deviation corresponded to 13% of the average value. It is concluded from this work that the Unitary Electric Power Method, as it encompasses more criteria pertinent to the generation process, appears to be the most conservative and is in line with what actually happens with the hydroelectric plant, being the MME method for a very optimistic. Therefore, this method may be important for more careful analyzes in relation to PG. In addition, it was evident that the use of average daily flows significantly influences the PG result by better portraying water availability and that a cautious assessment must be made in relation to the length of the series of flows because, depending on its length, some behaviors and trends availability may go unnoticed.