## 4 Results and Discussion
### Tracking Performance of an SDC System Running in Different Regions under Azimuth Axis Tilt Error  
With the maturity of solar photo-thermal power generation technology, its application in various parts of the world is also increasing rapidly. An SDC system needs to track the sun's position with high precision in order to ensure its power generation efficiency. However, the sun's position (the azimuth and elevation angles) is different in different regions, and the tracking performance of SDC systems is also different. Therefore, it is necessary to study the influence law of the SDC system running in different regions on its performance. This section mainly analyzes the influence of an SDC system running in different regions (Dunhuang, Naqu, Delingha, Kunming, Bootou, and Haerbin) on its tracking performance on a typical day (the summer solstice). The latitudes and longitudes of different regions are shown in Table 2.  
Figure 9 shows the variation of the effective tracking factor of an SDC system in different regions under the azimuth axis tilt error. Obviously, at different azimuth axis tangential angles, the effective tracking factors of the SDC systems in Bootou and Haerbin are relatively small, i.e., the tracking performance is relatively poor. The tracking performance is the worst when the azimuth axis tangential angle \(\phi_{1}=90^{\circ}\) (due west) or \(\phi_{1}=270^{\circ}\) (due east). The tracking performance is best when the azimuth axis tangential angle \(\phi_{1}=15^{\circ}\) (i.e., \(15^{\circ}\) south by west). Figure 10 shows the daily average effective tracking factors \(\overline{\sigma}_{\rm d}\) and \(\rm SD_{d}\) variations for different regions, and the specific data are shown in Table 2. It is obvious to see that the daily average effective tracking factors of Bootou and Haerbin are smaller and the \(\rm SD_{d}\) is larger, i.e., the tracking performance is relatively poor and the tracking \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & \multicolumn{5}{c}{**Regions**} \\ \cline{2-7}  & **Dunhuang** & **Naqu** & **Delingha** & **Kunming** & **Bootou** & **Haerbin** \\ \hline Latitude & 40.13\({}^{\circ}\) N & 31.29\({}^{\circ}\) N & 37.22\({}^{\circ}\) N & 25\({}^{\circ}\) N & 40.32\({}^{\circ}\) N & 45.42\({}^{\circ}\) N \\ Longitude & 94.67\({}^{\circ}\) E & 92.04\({}^{\circ}\) E & 97.23\({}^{\circ}\) E & 102.39\({}^{\circ}\) E & 109.53\({}^{\circ}\) E & 125.15\({}^{\circ}\) E \\ \(\overline{\sigma}_{\rm d}\) & 0.57234 & 0.5868 & 0.56715 & 0.58612 & 0.53792 & 0.49776 \\ \(\rm SD_{d}\) & 0.04874 & 0.04935 & 0.05539 & 0.06537 & 0.07072 & 0.08238 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Latitude and longitude and the daily average effective tracking factor \(\overline{\sigma}_{\rm d}\) and \(\rm SD_{d}\) of SDC systems in different regions. Figure 8: Variation of the daily average effective tracking factor \(\overline{\sigma}_{\rm d}\) and \(\rm SD_{d}\) of an SDC system with initial tracking position offset. performance stability is relatively low compared with other regions. From Table 2, we can find that the longitude of the Kunming region is not the lowest compared with other regions, but it has the lowest latitude. The tracking performance and tracking performance stability of an SDC system in Kunming's operations are better than that of Baotou and Haerbin. Compared with Baotou, although the latitude of Dunhuang is closer, the longitude of Dunhuang is lower, and so the tracking performance and tracking performance stability of the SDC system in Dunhuang are better. In summary, latitude is the main factor that determines the tracking performance and stability of an SDC system in different areas and longitude is the secondary factor. If a  
Figure 10: Variation of the daily average effective tracking factor \(\overline{\sigma}_{\text{d}}\) and \(\text{SD}_{\text{d}}\) of an SDC system in different regions. Figure 9: Variation of the effective tracking factor \(\sigma\) of an SDC system in different areas under an azimuth axis tilt error.