Cost-effective and portable device for partial shading assessment in photovoltaic modules using RGB imaging

Partial shading conditions in photovoltaic systems can cause major loss in performance. Therefore, models to estimate the reduction and distribution of irradiance due to partial shading are important to evaluate and minimize losses. In this paper, a model to estimate the irradiance reduction under partial shading conditions on PV installations is discussed. The proposed approach utilizes RGB images in the visible spectrum to estimate irradiance within the shaded areas of individual modules. The results suggest that there is a significant correlation between gray scale levels and irradiance in the shaded area. The conclusion is based on comprehensive observations and data collected during the experimental phase, which demonstrate regularity in irradiance values within the shaded area. The key advantage of the proposed methodology is its practical framework, which enables it to address various problems and types of partial shading, regardless of the complexity of the geometry. Furthermore, a model was proposed and validated based on this methodology. It is demonstrated that considering partial shading through RGB images, and by employing segmentation, homogenization, and regression using analytic models, this leads to an estimation accuracy in the irradiance parameter (RMSE of ∼1 %) of 11.14 W/m². This innovative methodology eliminates the need for multiple irradiance sensors or an IV curve tracer to map shadowed zones.