Statistical Analysis of Solar Radiation Data

Abstract

Solar radiation is the most important parameter in the design and study of solar energy conversion devices. The present work is based on statistical analysis of solar radiation data for the city of Valparaiso in the coast region of Chile. Ex perimental data were obtained from the Santa Maria University in Valparaiso over a five-year period measured by the actinograph and the pyranometer. The error between the actinography values in relation to the pyranometer ones was determined. The most frequent error percent for the actinograph was from 10% to 20% and it corresponds to the 56% of the days of the year. The greatest error frequency is estimated in the solar radiation range between 3001—4000 Wh/m², which corresponds to the 21% of the days of the year. Solar radiation data in Chile exists from about the 1960's; however, due to the inaccuracy of the measuring equipment, the enginery calculations have overestimation errors in the calculated area to be exposed to the sun. Those errors may imply overestimations around 15%; this is why the determination of a measurement error is necessary to correct the values and incorporate them to a more precise economical analysis.

Keywords:

• actinographs
• global solar radiation
• pyranometers
• solar radiation data
• statistical analysis

Acknowledgments

Special thanks to Mr. Roberto Sota and Mr. Rafael Bolocco of the Laboratorio de Evaluación Solar in the Universidad Federico Santa María, Chile. Dedicated to Prof. Dr. Ing. Pedro Roth for a whole life devoted to the solar energy in Chile.