# Simulation-Based Shading Loss Analysis of a Shingled String for High-Density Photovoltaic Modules
## 3 Results and Discussion
### Shading Characteristics of Shingled PV Module  
Figure 15 shows an image of the shading characteristics of the shingled PV module on which the measurements were carried out. The shading characteristics of the shingled PV module were measured by increasing the shading from 0% to 50% in increments of approximately 10%. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**No Shading**} & \multicolumn{2}{c}{**Bottom 5 cm**} & \multicolumn{2}{c}{**Bottom 10 cm**} & \multicolumn{2}{c}{**Bottom 1 Cell**} \\  & & **Shading** & **Shading** & **Size Shading** \\ \hline Size (cm\({}^{2}\)) & 19,403.52 & 19,403.52 & 19,403.52 & 19,403.52 \\ I\({}_{\text{sc}}\) (A) & 9.79 & 7.08 & 3.26 & 0.08 \\ V\({}_{\text{oc}}\) (V) & 48.70 & 48.45 & 48.38 & 47.66 \\ FF (\%) & 77.14 & 82.56 & 86.55 & 44.78 \\ Eff (\%) & 18.96 & 14.61 & 7.05 & 0.09 \\ P\({}_{\text{m}}\) (W) & 367.97 & 283.50 & 136.88 & 1.777 \\ Power ratio (\%) & 100 & 77.04 & 37.19 & 0.48 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Dependence of the measured shading characteristics of conventional PV modules on the amount of shading. Figure 14: Image of the conventional PV module used for measuring the shading characteristics for various amounts of shading at the bottom. Figure 15: Image of the shingled PV module that was used for measuring the shading characteristics by varying the amount of bottom shading. Table 7 lists the measured shading characteristics of the shingled PV modules. The measured results indicate that the output continuously decreased until 30% of the module was shaded, after which the output stabilized. The shading characteristics of the shingled PV module shaded at the bottom were more favorable than those of the conventional module. In the case of a shingled PV module, the shingled string itself has a higher voltage characteristic than a solar cell, so a shingled PV module can be manufactured by connecting each shingled string in parallel. As a result of this characteristic, the current mismatch is reduced even though the lower part is shaded, and thus the output loss is reduced. This can be analyzed through the fact that there is no change in the short-circuit current even though the shingled string occurs in the lower shadow. In comparison, since the shingled string is manufactured by connecting several divided cells in series cells, most of the shading loss in the shingled string appears as output loss due to current reduction or current mismatch. As a result, when the shaded area covered 30% or more of the shingled PV modules, the output stabilized at approximately 47% and did not decrease any further. This is because the bypass diode installed in the shingled PV module operates and bypasses the bottom parallel structure. The PSpice simulation of the shingled PV module was performed by changing the value of V\({}_{\rm input}\) of the divided cell affected by shading. Table 8 presents the simulated results of the shading characteristics of the shingled PV module. These results show that the maximum error rate of the measured characteristics of the shingled PV module and the power ratio value was approximately 0.65, and the output decreased with a similar trend. Similarly, when the amount of shade covering the bottom of the module was 30% or higher, the bypass diode operated, resulting in a similar output with a power ratio of less than 1%. As a result, in this study, the shading characteristics generated from shingled strings to shingled PV modules were analyzed and compared with those of conventional modules. In addition, PSpice modeling was performed to analyze the shading characteristics of the shingled PV module, and it was confirmed that the error in the power ratio remained within 1%. A graph comparing the power rate between the simulation and the measured value is