## 4 Results and Discussion  
### Performance Ratio  
Figure 5 presents an example of daily performance ratios of a selected PV system, a p-Si system in Cirata, during the year of 2017. The performance ratio, PR, is shown in blue, PRstc, in orange,  
Figure 4: Examples of the degradation rate of a copper indium gallium selenide (CIGS) PV system from Site 27 in Alice Springs. The degradation calculation based on (**a**) measurement sensors, and (**b**) a clear sky model.  
and PR\({}_{\text{ann}}\). in green. Scatter plots are the actual values, and the lines are the 30-day averaged values. As shown, the PR and PR\({}_{\text{ann}}\). values are close together while the PR\({}_{\text{qtc}}\). values are higher, about 0.1.  
In Figure 6, the performance ratios for each PV system, together with their mean values and standard deviation (std), are shown. In each subplot, the blue box plot to the left is the PR value. The middle orange plot is the PR\({}_{\text{stc}}\). value. The right green plot is the PR\({}_{\text{ann}}\) value. As shown, the mean values of PR were slightly higher than PR\({}_{\text{ann}}\), with around a 0.4% difference. However, PR\({}_{\text{ann}}\) had a narrower standard deviation by 30% compared to the standard deviation of PR because its seasonal variations due to the temperature effect had been reduced using annual-averaged temperature values. The PR\({}_{\text{stc}}\) values were always the biggest among the two other PRs (around 10% higher) because they were estimated with an STC temperature of 25 \({}^{\circ}\)C.  
Figure 5: Daily performance ratio of a p-Si system in Cirata in 2017.  
Figure 6: Box plots of the performance ratio of each PV system. Left/blue: PR, middle/orange: temperature-corrected PR by STC, right/green: annual-averaged temperature-corrected PR. Numbers at the upper right corners in the boxes indicate the duration of the analyzed data in the number of years.  
Figure 7 shows the mean performance ratio and its standard deviation by technology. The CIGS module has the highest values of all PR types, followed by HIT. The performance superiority of CIGS and HIT modules were also reported in Thailand, which has a tropical climate as well [12]. The p-Si and CdTe modules follow in terms of the values of PR and PR\({}_{\text{ann}}\). However, when the temperature is closer to STC, p-Si modules performed better than CdTe modules. In addition, the performance range of p-Si modules is smaller than CdTe modules. A similar comparison was observed for mono-Si and a-Si modules in terms of STC temperature; the mono-Si modules had a higher PR than a-Si while their PR and PR\({}_{\text{ann}}\). were relatively similar.  
Table 2 shows the performance ratio and their standard deviation by climate. For the climatic comparison of PRs, we use p-Si modules because 50% of the evaluated PV systems fall in this category. In terms of PR and PR\({}_{\text{ann}}\)., the p-Si system in climate Cfb of Italy has a higher performance of 0.84 than those in climates BWh (Australia) and Af (Indonesia) with the same value of 0.81. In contrast, PR\({}_{\text{stc}}\). in climates BWh and Af were slightly higher than those in climate Cfb. The reason for this is because the average temperature in climates BWh and Af are closer to 25 \({}^{\circ}\)C.