Enio Bueno Pereira

Survey of the incident solar radiation in Brazil by use of meteosat satellite data

Abstract Meteosat-2 satellite data in the visible band were used to calculate monthly averages from daily mean incident solar radiation over Brazil, using the IGMK physical model for the period 1985–1986. Satellite estimates are compared with ground data from 22 national stations. The global root mean square error between model and ground results for all data points was 13%, and the mean bias error was 1.23 MJ m −2 . About 68% of the individual errors were below 10% and clustered around 8%. Global radiation estimated by the model ranged from 9.0 to 27 MJ m −2 with the diffuse to global ratio falling into the 0.2–0.5 interval. Enhanced inverted zonal trends were found for both satellite predictions and the ground station results.

BRAZILIAN ATLAS FOR SOLAR ENERGY RESOURCE: SWERA RESULTS

The solar energy assessment in SWERA project was prepared by using BRASIL-SR radiative transfer model and satellite database acquired from 1995 till 2005 – a full decade dataset. The annual and seasonal maps prepared were in 10X10km spatial resolution. In spite of the different climate characteristics along the Brazilian territory, one can observe that the annual average of daily solar irradiation is fairly uniform. The maximum daily global solar irradiation value (6.5 kWh/m2) occurs in the semi-arid climate area of Brazilian Northeastern region. The lowest daily global solar irradiation (4.25 kWh/m2) occurs on the shore of Southern region of Brazil. The Amazon region receives lower solar irradiation during the summer than the Southern region. The variation of the solar irradiation between winter and summer is smaller in the Northern region than in the Southern. The Central region of Brazil gets a larger incidence of solar radiation during the dry season when the precipitation is low and the number of clear sky days is larger.

ESTUDO COMPARATIVO DA CONFIABILIDADE DE ESTIMATIVAS DE IRRADIAC ¸ ˜ AO SOLAR PARA O SUDESTE BRASILEIRO OBTIDAS A PARTIR DE DADOS DE SAT ´ ELITE E POR INTERPOLAC ¸ ˜ AO/EXTRAPOLAC ¸ ˜ AO DE DADOS DE SUPERFICIE

The exploitation of solar energy is becoming cost-effective, and currently is the renewable source showing the higher growth worldwide. The knowledge of solar energy resources is essential to boost new investments in solar systems for electricity generation. The estimation of site-specific solar irradiation, where ground data are not available, can be accomplished by two approaches: interpolation/extrapolation of surface measurements acquired at neighboring stations or by radiative transfer models based on satellite images. The choice between these two approaches depends on the evaluation of their uncertainties. In this study employed solar radiation data collected by 18 automatic weather stations (AWS) located in the Brazilian southeast region to extrapolate and interpolate solar irradiation at different distances from the AWS. Statistical analysis of the deviations as a function of the distance from the closest measurement site have shown that the root mean square errors (RMSE) increase as the interpolation/extrapolation distances increases. It was found that the greater the distance between AWSs and the reference site, the higher the deviations. Comparing the extrapolation/interpolation RMSE with the RMSE observed for estimates provided by the BRASIL-SR model, it was found that only for distances less than 60 km, the methods of interpolation and extrapolation showed deviations within the range achieved by using the satellite model. Thus, it is possible to conclude that the use of satellite data and radiative transfer models represent the best solution for the assessment of solar energy further from ground radiation measurement sites.