An empirical method for estimation of hourly diffuse fraction of global radiation

M. Al-Riahi, N. Al-Hamdani and K. Tahir

Renewable Energy, 1992, vol. 2, issue 4, 451-456

Abstract: Modelling of solar energy systems requires computation of both direct and diffuse components of incident solar radiation. Based on data collected between 1984 and 1987 in Fudhaliyah near Baghdad, a correlation is developed to estimate the diffuse fraction of hourly global radiation in terms of clearness index. Results show that this correlation is very comparable to correlations suggested by other studies. Because this correlation gives a significant uncertainty in the estimated hourly diffuse radiation, a new empirical multiparameter correlation is proposed. In this new method, hourly diffuse radiation is derived from hourly clearness index and intensity of sunshine. Comparison of predicted and measured values indicate the method performs well during different sky conditions. The statistical distribution shows that 88.5% of the estimated diffuse radiation lies within a small error (±0.2 MJ/m2). The peak of the error frequency histogram occurs for the class of −0.1 to 0.0 MJ/m2, and the error distribution is almost symmetrical about zero.

Date: 1992
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:2:y:1992:i:4:p:451-456

DOI: 10.1016/0960-1481(92)90079-I

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