Encontro de Energia no Meio Rural

Abstract

RECIERI, Reinaldo Prandini, KOEHLER, Karina, KOEHLER, Ana Caroline et al. Modelos de estimativa da radiação difusa diária em Cascavel. In Procedings of the 4th Encontro de Energia no Meio Rural, 2002, Campinas (SP) [online]. 2002 [cited 25 April 2024]. Available from: <http://www.proceedings.scielo.br/scielo.php?script=sci_arttext&pid=MSC0000000022002000200029&lng=en&nrm=iso> .

In this work we evaluate, by means of polynomial and transcendental regression analysis, several models that relate the diffuse fraction of the global radiation (K_d) with the clearness index (K_t). The experiment was conducted in the Solar Radiometry Station of Cascavel/Pr from the first of January to the 31^st of December, in the year of 2001. The solar radiation components were monitored by the following manufactured instruments: Pyranometer (KIPP&ZONEN (CM3) and pirheliometer (EPPLEY NIP) connected in a sun tracker (ST-1 model). A datalogger CR10X from the CAMPBELL SCIENTIFIC Inc. was used in the data acquisition. This datalogger was programmed in the frequency of 1 Hz storing an average of 5 minutes of collected data. The distribution of daily values for the relation K_d X K_t, find by regression analysis, provided equations with right values of determination coefficients. Among the polynomial equations the best values of RMSE an MBE were find in the 4^th, 3^rd, 2^nd and 1^st degrees, respectively. We also find that the 4^th degree polynomial equation ( K_d=1,172-1,001K_t+3,992K_t²-11,742K _t³+7,698K_t⁴) generalizes the utilization of equations for diffuse solar radiation estimation. This means that this equation probably can be applied for any place and climatic conditions.

Keywords : radiação solar difusa; modelos de estimativa; índice de claridade.