Assessing the impact of diffuse fraction estimation on ground albedo modeling.

Abstract

Ground reflectivity or albedo is required for the estimation of the solar irradiance incident on an inclined surface. The ground is frequently modeled as a constant albedo diffuse reflector and this is inadequate for several solar energy applications, particularly for bifacial PV power plant yield estimation. Recent advances have categorized albedo models according to their complexity, with bivariate models -those incorporating the zenith angle and diffuse fraction- performing better. In a previous study, Rodríguez-Muñoz et al. (2022) evaluated six albedo models and confirmed that bivariate models were the most accurate. However, they also highlighted the need for measurements of both global and diffuse solar irradiance to apply these models. For simplicity, empirical diffuse fraction models can be used instead of using diffuse irradiance measurements. This study builds upon prior research by assessing the impact of employing empirical diffuse fraction models on albedo estimation. To assess this, measurements were conducted over the course of approximately one year at an experimental site with soil and climate conditions representative of the Pampa Húmeda region in South America. The results indicate that incorporating these models into albedo estimation slightly degrades performance, but still outperforms constant and univariate models. Thus, a bivariate albedo model combined with diffuse fraction estimates represents an effective balance between accuracy and simplicity.