Adapting the Spencer model for diffuse solar radiation in Badajoz (Spain)

摘要

Reliable estimations of solar global radiation and its partitioning direct‐to‐diffuse are demanded forthe use of solar energy as renewable energy source. While solar global radiation is widely available atradiometric stations, measurements of the diffuse component are rather scarce. Therefore, soundmodels to obtain reliable estimations of the partitioning direct‐to‐diffuse are required. In this study,the Spencer's model is applied to original measurements performed at a radiometric station inBadajoz (Spain). This model proposes a linear relationship between the ratio diffuse to global solarradiation and the clearness index, defined as the ratio solar global irradiance at ground level to solarirradiance at the top of the atmosphere. Additionally, the regression coefficients were computed andcompared to those proposed by Spencer for our latitude. Results indicate that Spencer's modelreflects the general trend of the measurements. The calculated regression coefficients are similar tothose proposed by Spencer, showing relative differences between 0.3% and 20%.