The Importance of Diffuse Irradiance Data on the Designing And Evaluation of PV Tracking Strategies Developed for Any Sky Conditions

Solar trackers have traditionally been programmed to keep modules as perpendicular as possible to the sun (astronomical tracking). However, the development of alternative tracking strategies that increase the amount of radiation received by the modules under any sky condition has become an increasingly relevant area of study. Evaluating the energy performance of such strategies at a given site requires detailed knowledge of the site’s irradiance conditions. This information can be obtained from various databases, though many of them provide diffuse irradiance values that are estimated from satellite imagery or derived from global irradiance measurements. This paper demonstrates the importance of using measured, rather than estimated, diffuse irradiance data in this type of study. Using two different databases—one containing measured diffuse irradiance values and the other containing estimated values—we calculated the potential radiation gain that could be achieved by a horizontal single-axis tracker when, instead of following astronomical tracking, its position is continuously adjusted to maximize the irradiance on the module plane. The results reveal significantly different radiation gains depending on the database used. In fact, the gain calculated using the dataset with measured diffuse irradiance values is nearly twice as high as that obtained using the dataset with estimated diffuse values.