# Experimental Investigation of the BIPV System under Sanluurfa Meteorological Conditions
## 3 Results and Discussion  
The data collected from the experiment conducted on 5 May 2023, between 7:00 a.m. and 7:00 p.m., with intervals of 30 min, regarding solar radiation (W/m\({}^{2}\)) and electricity energy production (W), are presented in Figure 4. On the east-facing panel, the power generated in the early hours of the day reached 211.3 W at 8:00 a.m. and then decreased toward 12:00 p.m. The electrical efficiency of the panel placed on the east facade was found to be an average of 15.98% daily. The total energy produced daily was 1.09 kWh. For the panel on the roof, as the sun rose, both radiation and power production increased. The highest power production was measured at 240.4 W at 12:00 p.m. As the sun was setting, production decreased. The electrical efficiency of the panel on the roof was found to be an average of 15.65%, and the total daily energy produced was 1.95 kWh. The panel on the roof produced 79% more electrical energy on this date than the panel on the east-facing side. On the south facade, both the monofacial and bifacial panels increased their production parallel to the radiation values as the sun rose, and at 12:00, the monofacial panel produced a maximum power of 128.3 W, while the bifacial panel produced 149.6 W. In the subsequent hours, these values began to decrease. At the hour with the highest power generation of the day, the bifacial panel produced 16.6% more electrical power than the monofacial panel. As seen in Figure 4, the power production curve of the bifacial panel followed a higher trajectory compared with the monofacial panel under the same conditions on the south facade. On this facade, the daily average electrical efficiency of the monofacial panel was 17.53%, while the bifacial panel's average efficiency was found to be 20.54%. The increased production of the bifacial panel compared with the monofacial panel was supported by a 2.9% power difference in the study conducted by [PERSON] et al. (2021) [34]. Because of the influence of its rear surface, the highest efficiency among the four panels was observed in the bifacial panel. In terms of daily average efficiency, the bifacial panel showed a 17.1% gain compared with the monofacial panel on the same facade. In our study, the bifacial panel showed a higher performance compared with the bifacial panel tested in the study by [PERSON] et al. (2021) [34]. Additionally, when comparing the total amount of daily  
Figure 4: Power and radiation data produced by the experimental setup on 5 May 2023.  
generated energy, the bifacial panel produced 1.04 kWh of energy, while the monofacial panel on the south side produced 0.886 kWh on the same day. Here, too, it was found that the bifacial panel produced 17.3% more energy. Because of the Sun hitting the Earth at a steeper angle on 5 May compared with the winter months, the highest electricity production on the roof was observed on this date. It was observed that the superiority of the bifacial panel's performance is higher compared with the monofacial panel of the same capacity, and its use in BIPV systems can make production more efficient. In the experimental setup, the monthly electrical energy data produced in February, March, April, May, June, and July, as well as the error rates of the PVsyst analysis, are provided in Table 2. Because of Sanluirra's location in the northern hemisphere, in February, the south-facing facade achieved higher electricity production compared with other facades, as observed in Table 2 and supported by [PERSON] et al. (2012) [13]. During the spring and summer months, a higher level of production was achieved on the roof than on other facades. Additionally, it was observed that the bifacial panel produced more electrical energy compared with the monofacial panel by 11% in February, 11.66% in March, 13.56% in April, 16.16% in May, 22.61% in June, and 19% in July.