Análise da variabilidade e similaridade da velocidade do vento no Nordeste do Brasil

Abstract

The use of renewable energy sources has grown worldwide and in Brazil the incentive to use wind energy has been expanding significantly. Currently, the country stands out in the global wind scenario occupying the ninth position among the countries with largest installed capacity of accumulated wind power, leading the Latin American market. The Northeast (NE) has the highest wind potential in the country. However, there is a great variability in wind speed due to climatic diversity. The NE is divided into four sub-regions, Litoral, Agreste, Sertão e Meio Norte. There are different institutions that provide wind speed data, essential variable to study, related to deployment and wind power generation. This study analyzed wind speed time series coming from two different database, INMET and ERA-40. The records provided by INMET were obtained by conventional stations at 10 m above ground during the period from 1961 to 2001 at 00, 12 and 18h. The historical series of ERA-40 belong to a global grid with spatial resolution of 2.5 × 2.5 records at 10 m above ground at 00, 06, 12, 18h during the period from 1957 to 2001. The objective is to study spatial and temporal variability of wind speed and to measure the degree of similarity between the conventional stations (INMET) and reanalysis (ERA-40) database in order to quantify the degree of regularity of the time series and the degree of similarity between two time series using the methods Sample Entropy and cross-Sample Entropy of information theory. Due to lack of information on the basis of INMET, analyzes were performed on eight years of simultaneous data (1993 to 2000) to the database INMET and ERA-40, for the series of 00h, 12h, Full/Total (original series) and Daily (average per day). The results show that the highest wind speed records for different series are in the North of the four sub-regions. The Sample Entropy showed highest wind speed regularity in Meio Norte, where the wind speed is lower, with better predictability. The cross-Sample Entropy showed that there is moderate synchronization between the series INMET and ERA-40, indicating an overestimation or underestimation of ERA-40 data in relation to INMET data. The Meio Norte is the region with highest similarity between INMET and ERA-40 series. Examining the regularity of ERA-40 through all the observations from 1957 to 2001 using the Sample Entropy, it was found that the regions with higher wind speed have better predictability of wind speed temporal series, and that different regions with similar mean wind speed can have a different predictability.