Experimentally diagnosing the shading impact on the power performance of a PV system in Hong Kong

This paper presents an experimental diagnosis on the power performance of a PV system in Hong Kong. The annual solar radiation received by the PV modules was simulated based on the recorded horizontal solar radiation. The theoretical annual energy output of this PV system was about 11,702 kWh/yr, which was higher than the actual energy output by 24.5%. In order to find out the reasons of the energy loss, an on-site inspection and testing was conducted. The shading and aging problems were found in the process of visual inspection. The shading problem can be further subdivided into edge-shading, pillar-shading and nameplate shading. To further understand and quantify the impact of different types of shadings on the power output performance, the I-V curves of a PV module were tested under different solar radiation. The testing results showed that the impact of different types of shadings on the power performance varied with the Sun position, solar radiation as well as the time. In general, the edge-shading effect reduced the energy output of PV system by 11%-15% the pillar-shading effect reduced the energy output by 15%-19%, and both effects of edge-shading and pillar-shading reduced the energy output of PV system by 18%-35%. Thus, the main reason that resulted in the energy loss of this PV system was attributed to the shading impact. If the edge-shading and pillar-shading problems are solved, the annual energy output of the PV system could increase about 20%-24%.