## 1 Introduction
To study the interaction between PV systems and their surrounding environment, CFD simulation methods have been widely applied [21; 22]. With the continuous advancement of numerical algorithms and computational power, CFD has become a reliable and widely used research method across various fields, including PV system analysis. And the airflow above/around photovoltaic (PV) panels and the air gap between PV panels and the building envelope are key topics of discussion in this field [23]. At the same time, enhancing the natural ventilation of rooftop PV systems can improve PV panel cooling. The authors of [24] employed the standard k-\(\epsilon\) turbulence model to describe turbulent natural convection. Through numerical studies, they explored the impact of natural convection air cooling on the performance of a novel hybrid photovoltaic/thermal (PV/T) collector. The findingsindicated that increasing the tilt angle of the PV/T system can enhance airflow velocity, thereby improving cooling efficiency. CFD simulation is also widely used in the natural ventilation design of substations [10]. Through numerical modeling and CFD simulation research, the air inlet design of an indoor substation can be optimized to enhance natural ventilation and reduce the dependence on mechanical ventilation, thus reducing the carbon emission of the substation [25]. Natural ventilation can improve heat dissipation in high-temperature, high-load indoor substations, but improper design may interfere with the main air intake of the exhaust fans, leading to low cooling efficiency [26]. The feasibility of natural ventilation in substation control buildings located in cold regions during summer and transitional seasons has been demonstrated using CFD methods [27]. Using CFD simulations, the ventilation and heat dissipation of a semi-indoor substation main transformer room are analyzed and optimized. Reference [17] evaluates the impact of air inlet angles on the velocity distribution, temperature distribution, and airflow rate. The impact of PV system installations on the wind environment of substations is relatively underexplored. However, semi-outdoor substations are highly sensitive to natural ventilation, making it essential to use CFD simulations to assess how PV systems affect such substations. The design of the PV system above the semi-outdoor main transformer room is of critical importance, requiring a balance between ventilation efficiency, energy consumption, and maintenance convenience. Considering local climatic factors, such as wind direction, wind speed, and rainfall, is essential to ensure that the PV system does not negatively impact the ventilation of the main transformer room while maximizing the utilization of these natural factors to enhance both ventilation efficiency and PV power generation. Accurately assessing the impact of PV panel arrangements on airflow is crucial, given the specific operational requirements and internal spatial structure of the main transformer room. Traditional rooftop PV designs typically focus only on factors affecting power generation, such as building orientation, local latitude, and solar resources, while overlooking the impact of PV systems on rooftop wind environments and indoor natural ventilation. Existing substation construction guidelines provide ambiguous instructions regarding PV panel placement, and research in this area is significantly lacking. Therefore, this study introduces an optimized rooftop PV system strategy aimed at maximizing PV generation capacity without compromising the natural ventilation of the main transformer room. This study evaluates the effects of the orientation, tilt angle, and arrangement of PV panels on natural ventilation airflow within the main transformer room and PV power output. The objective is to determine the most effective PV panel layout to enhance both rooftop PV system performance and natural ventilation efficiency within the main transformer room.