Empirical models for estimation of diffuse solar radiation in a tropical, mountainous and humid place (Xalapa, México)

Abstract

[ES]Para estimar la radiación difusa horizontal en un sitio de clima tropical y montañoso, se presenta una selección de polinomios empíricos. Para generarlos se usaron datos registrados cada 10 minutos entre julio 2011 y junio 2012. Las variables independientes son el índice Kt (cociente de radiación solar global entre extraterrestre) y el Kd (cociente de radiación difusa entre radiación global). Las temperaturas máximas y mínimas y la precipitación diarias, se usaron como discriminantes en agrupaciones de casos para mejorar la bondad de ajuste de los modelos. Los polinomios tienen validez mensual, trimestral, semestral o anual, y no son aplicables a condiciones de cielo completamente nublado o completamente despejado.

[EN]In order to estimate the horizontal component of diffuse solar radiation in a tropical, mountainous, and humid place, a selection of empirical polynomial models is presented which was obtained by statistical regression. The data of global and diffuse irradiance were captured every 10-min from July 2011 to June 2012. The independent variables are the clearness index (Kt, the ratio of global radiation over extraterrestrial radiation), and the diffuse fraction (Kd, the ratio of diffuse radiation over global radiation). Daily temperatures as well as rainfall were used to cluster cases and thus improve the goodness of fit of the empirical models. The models have a monthly, quarterly, semi-annual or annual validity, but are mostly not applicable to cloudy or clear sky conditions.