Impacts of shadow conditions on solar PV array performance: A full-scale experimental and empirical study

Abstract

Shadow is an important hurdle to the power generation efficiency of solar photovoltaic (PV) modules. So far, most previous studies on this aspect have focused on simulation, lacking full-scale experimental study, not to mention the relevant quantitative experimental analysis. Therefore, this study conducted a full-scale outdoor experimental and empirical study on the PV modules under different shadow conditions. Experimental results revealed that the power generation capacity of a single-string PV module decreases by approximately 90 % when a specific solar cell is entirely obstructed. When a cell is shadowed, the short-circuit current drops by 20–25 %. The open-circuit voltage (V_oc) drops by 25–30 % when 2/3 of the PV modules are shadowed. The short-circuit current (I_sc) has a linear relationship with a smaller shadow less than a solar cell, and the V_oc has a linear relationship with a shadow larger than a solar cell. However, the power generation efficiency exhibits a nonlinear relationship with the shadow ratio of the cells when they are subjected to shading. Based on the full-scale experimental tests, this study developed an empirical model, for the first time, to address the relationship between shadow ratio and power generation efficiency, where the power generation efficiency is negatively related to the 3/2 power of the shadow area. The obtained research outcome, together with the empirical model, can pave the way for future large-scale (e.g., global scale) study on addressing the impact of shadow conditions (e.g., bird droppings, dark clouds, gravel, and dust) on the power generation of solar PV systems.