6533b822fe1ef96bd127cb9d

RESEARCH PRODUCT

A very simple model for computing global solar radiation

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Abstract In this paper a very simple model for predicting the daily global solar radiation at any Italian location using as input of a few extensively measured meterological parameters is proposed. In fact the daily radiation G (MJ m−2) is here correlated only with the sunshine duration s (h) and the noon altitude of the sun on the 15th of the month h n (degrees) by the following equation: G= Ks 0.5 (sin h n ) 1.15 where only one value of the factor K is used. The validity of this formula is verified fixing K = 7.8 and using the data from 34 Italian stations displaced at various latitudes, altitudes or geographical situations (inland or coastal site). The test results show that the deviations of computed values of G from measured ones are generally very low; the maximum error of estimates do not exceed 10% for all tested stations with exception of three locations (Napoli, Macerata and Pian Rosa) having very particular microclimates. Therefore these deviations become less than 10% assigning to factor K the values of 7.0, 9.7 and 11.7 for Napoli, Macerata and Pian Rosa, respectively. Consequently the very simple model proposed is suitable and useful to predict the daily global solar radiation at all Italian locations which lack actinometric instruments, independently of the latitude and the altitude of the place, with good reliability.