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Encontro de Energia no Meio Rural

#### Abstract

RECIERI, Reinaldo Prandini, QUALLIO, Silvana, FERRUZZI, Yuri* et al*. **Models in the estimate of the diffuse solar radiation**.
In
* Procedings of the 5th Encontro de Energia no Meio Rural, *2004, Campinas (SP)
[online].
2004 [cited 04 November 2024].
Available from:
<http://www.proceedings.scielo.br/scielo.php?script=sci_arttext&pid=MSC0000000022004000200022&lng=en&nrm=iso>
.

In this work we evaluate, by means of polynomial 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 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. Among the equations the best values of RMSE an MBE were find in the 4^{th} and 3^{rd} 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; Modelo de estimativa; índice de claridade.