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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 28 May 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_{t}^{2}-11,742K_{ t}^{3}+7,698K_{t}^{4}) 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.