Encontro de Energia no Meio Rural

Abstract

TIBA, Chigueru. Novos coeficientes de angstrom para a estimação da radiação solar no Nordeste do Brasil. In Procedings of the 4th Encontro de Energia no Meio Rural, 2002, Campinas (SP) [online]. 2002 [cited 19 April 2024]. Available from: <http://www.proceedings.scielo.br/scielo.php?script=sci_arttext&pid=MSC0000000022002000200030&lng=en&nrm=iso> .

Information about solar radiation in Brazil is scarce and has presented problems in quality, and spatial and temporal fragmentation , as well , as it can be seen in a recent publication named Atlas Solarimétrico do Brasil - Dados Terrestres (Tiba et al., 2001). ( Solarimetric Atlas of Brazil - Terrestrial Data ) . This Atlas is a compendium of solarimetric information - solar radiation and insolation - presented in a standardised and evaluated way. Consulting this data base has permitted the identification of 35 locals in the Northeast region , with simultaneous registers of average daily and monthly solar radiation and sunshine hours. Such information was used to calculate the Angstrom Linear Regression coefficients (named a and b) that, were also used for making regional maps of isolines of the a and b coefficients by the use of geo-statistic interpolation known as Kriging. An statistical checking of the precision of solar radiation estimates, produced with the use of these maps, was made too , comparing them with the pyranometer data of the Instituto Nacional de Meteorologia. In a general way, the Angstrom correlation functions very well with the local coefficients deduced from the isoline maps of a and b. The mean-square errors of these predictions are, at most, 6.6 % , or be it, below the measurement errors of a 8-48 Model B&W Eplley pyranometer field , that are about 7.5 % . The use of Angstrom local coefficients inferred from the maps has permitted the solar radiation estimates also in other 60 locals of the Northeast of Brazil.

Keywords : Radiação solar; Insolação; Correlação de Angstrom; Kriging; Projeto de Sistema Fotovoltaico.