## 6 Discussion and Conclusions
The analysis results of the output of each PV array showed that more than half of the output values measured over a year were below 6.7(%) of the rated capacity of PCS. This caused a deterioration of the conversion efficiency of the PCS. An analysis of the annual conversion efficiency of each PV array, showed that SI 30\({}^{\circ}\), which is a favorable condition for receiving intense irradiation compared to other PV arrays, showed the highest efficiency of 84.7(%), followed in order by HR 0\({}^{\circ}\) (83.6(%)), SV 90\({}^{\circ}\) (81.3(%)), and WV 90\({}^{\circ}\) (80.3(%)). These results indicated that the conversion efficiency of the PCS decreased as the solar irradiation conditions become less favorable. When PR was calculated, assuming the PCS performance when it operates normally, it showed an increase of 4.1(%) to 8.0(%). The optimal installation condition for South Korea PV system is the southward inclination angle of 30. However, it is very difficult to install the BIPV system under optimum installation conditions except for the case where it is installed on the roof or the rooftop of the building. In addition, since the BIPV system is installed mainly on the elevation of the building, the installation azimuth of the PV array is also limited. For this reason, the BIPV system generates less power than the PV system. There is a limit to the increase of power generated by the BIPV system. Therefore, it is necessary to pay attention to and manage the performance loss factors that may occur in its design and operation. The results of this study can quantitatively evaluate some performance factors that may arise from design to operation of BIPV system. Since the effect of the performance loss factor by the installation condition under the same environmental condition was evaluated, it was possible to derive the loss factor to be considered further according to the installation condition. In case of installation conditions with a high accumulated irradiance, it was confirmed that the power generation was large, but that the efficiency of the PV array was relatively lower. In case of installation conditions with low accumulated irradiation, the power generation was small, but the performance loss due to module temperature was also small. It is also expected that it will be able to maintain the design performance in the long term because the influence on dust and soiling is relatively low. In the case of performance loss due to the capacity mismatch of the PCS and the PV array, the installation condition with low accumulated irradiation was analyzed to have a large performance loss. The results of this study demonstrate the effects of the performance loss factors that can occur in general BIPV and PV systems, even though the degree of the impact may vary from region to region. Efforts are needed to maintain the design performance of the BIPV system through ongoing management from design to operation. Conceptualization, J.-H.Y. and H.-M.L. ; Formal Analysis, H.-M.L. ; Investigation, S.-C.K. and C.-S.L. ; Data Curation, H.-M.L. and S.-C.K. and C.-S.L. ; Writing--Original Draft Preparation, H.-M.L. ; Writing--Review & Editing, J.-H.Y. and C.-S.L. ; Visualization, H.-M.L. ; Supervision, J.-H.Y. ; Project Administration, J.-H.Y. This work was supported by the Korea Energy Agency (KEA) and by the Ministry of Trade, Industry and Energy (MOTIE) of the Republic of Korea (No. 71000151). This research was supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning (No. NRF-2016M1A2A2936758). The authors declare no conflict of interest.