ESTIMATE OF GLOBAL SOLAR RADIATION WITH AIR TEMPERATURE DATA IN SIX CITIES OF THE CEARÁ STATE, BRAZIL

Abstract

The global solar radiation is a major source of energy in the physical, chemical and biological processes can be measured by instruments such as radiometers, bimetallic actinographs and pyranometers. However, such measuring equipment of solar radiation are not available in most locations. Accordingly estimates, can be obtained with the use of mathematical models that use data only air temperature. That said, the aim of this study was to evaluate the performance of global solar radiation models, using maximum and minimum temperature air data to the cities of Barbalha, Campo Sales, Crateús, Jaguaribe, Iguatu and Quixeramobim in Ceará state, Brazil. Were used data of the global solar radiation and maximum temperature and minimum air obtained from the National Institute of Meteorology. The performance of the models was evaluated according to statistical indexes standard error estimated, mean and percentage error. With the lowest error values the best estimates of solar radiation were found in models of Hargreaves and Samani modified by Richardson and Ball et al. The worst results were found in models Donatelli and Campbell and Hargreaves and Samani.