Análise do impacto das incertezas hidrológicas na garantia física da geração hidrelétrica de pequenas centrais hidrelétricas

Abstract

Small Hydroelectric Plants (SHPs) make up 3.3% of the Brazilian electricity grid, and are becoming more popular given their lower environmental impacts compared to larger hydroelectric plants. The energy generated by SHPs is sold using a Physical Energy Guarantee, also known as a Power Purchase Agreement (PPA), which is the maximum amount of energy that a generator can sell. The PPA is calculated based on monthly average flow series data, however, studies have shown that this can overestimate the PPA, and that daily average flow series data are more accurate in reflecting the amount of generated electric energy. Unlike other hydrological evaluations, the uncertainty levels associated with the data used to calculate the PPA at SHPs are neither considered nor quantified. This study investigates the impact of hydrological uncertainties on SHP PPAs. The Monte Carlo method was used to analyze the uncertainty levels for an SHP case-study. The results showed that the PPA, in optimistic and pessimistic scenarios, was higher than the current PPA. Dispersion analysis revealed that SHPs with smaller installed capacities and lower PPAs faced more business risks, compared to SHPs with higher PPAs, which are generally more thoroughly evaluated by investors. It was verified that once the adhesion of the SHPs to the Energy Reallocation Mechanism (ERM) is optional, the analysis of the uncertainty margins of the PPA has the possibility of allowing the generator to have an additional mechanism for analysis and decision making regarding the adhesion or not to the ERM. With the uncertainty margins it is possible to compare if the value attributed by the Ministry of Mines and Energy is within the delimited margins, as well as allow the entrepreneur to evaluate in probabilistic terms the real generation conditions of its plant and the risks to be faced in terms of energy trading.