## 4 Results and Discussion
### Lessons Learned for PV Layouts in Semi-Outdoor Substations  
This section discussed the impact of different PV system configurations on indoor ventilation and now provides a deeper comparison with other related studies to highlight the specific application context of this research. The focus here is on how the PV panel layout affects the wind environment of the building. This study evaluates the influence of PV system installation on ventilation and cooling in the main transformer room to ensure that power generation performance is achieved without significantly compromising natural ventilation.  
The existing literature has begun to recognize the importance of jointly optimizing ventilation openings and PV layouts in industrial buildings to satisfy natural ventilation requirements. One study, which focused on adjusting rooftop vents and PV layouts in industrial workshops, showed that for naturally ventilated buildings, the form and position of rooftop vents had no significant effect on the indoor thermal environment, provided that the total exhaust area was maintained. ventilation volume dropped slightly by approximately 5% [19], but adjusting the roof structure and vent layout allowed for increased PV coverage. This is consistent with the findings in the present study, which observed that a horizontal PV layout led to a ventilation reduction of around 10%, while a well-designed system (e.g., 10\({}^{\circ}\) symmetrical layout) reduced the impact to just 0.6%. However, the mentioned study was conducted on enclosed industrial buildings with roofs and focused on repositioning ventilation openings rather than modifying the PV layout itself. In contrast, ventilation studies on substations have primarily focused on fully indoor substations. For example, the study titled An Investigation of the Ventilation Systems of Whole-Indoor Urban Substations developed a combined natural and mechanical ventilation  
Figure 9: Power generation: (**a**) photovoltaic system power generation and power generation loss; (**b**) photovoltaic self-shading loss.  
strategy to address high indoor temperatures. It concluded that improving ventilation--whether by reducing outdoor temperatures or increasing airflow--can effectively lower indoor temperatures [36]. Like the present study, it emphasized the importance of natural ventilation for cooling in substations. Another study using CFD to optimize the air inlet design of an indoor substation (110 kV) under natural ventilation found that a dual-inlet configuration improved cooling uniformity and avoided airflow decay. Compared to a single-inlet design, the dual-inlet layout reduced the maximum transformer temperature by 1.3 \({}^{\circ}\)C and improved energy utilization by 9.1% [26]. This aligns with the findings in this study, where symmetrical PV configurations function effectively as ventilation openings, offering the most balanced performance.  
To date, there has been limited research on how PV installation affects the wind environment in semi-outdoor substations. However, because semi-outdoor substations are highly sensitive to natural ventilation, using CFD simulations to assess the impact of PV systems is especially important. This research contributes new insights into the application of PV systems in semi-outdoor substations, filling an important gap in the existing literature.