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The objective of this work is to obtain a universal model for calculating the annual angular reflection losses (AAL) of PV modules working in real conditions, useful in the prediction or assessment of the annual performance of PV systems. Instantaneous angular losses (AL) can be calculated by using an analytical model, formerly developed by the authors, that has proved to be in good agreement with the experimental data. In this paper we have used this model to calculate AAL in an hourly basis at 79 different sites all over the world and considering ten different tilt angles, from horizontal to vertical, for south (north) oriented PV modules at north (south) hemisphere sites. From the analysis of the results, we propose an easy-to-use mathematical expression for the calculation of AAL. The model has three different versions that are to be used depending on the availability of the local radiation data. The most detailed expression of the model fits with high degree of accuracy the local AAL data, the second version consists of a global term plus a local weather-descriptive one, and the third version is a universal global model dependent only on the latitude and the PV module tilt angle. Copyright © 2004 John Wiley & Sons, Ltd.
Martín et al. (Tue,) studied this question.