Multiscale assessment of thermal regulation and regional energy performance in ventilated photovoltaic façades

Façade building-integrated photovoltaics (BIPV) with ventilated cavities can affect both photovoltaic thermal performance and building energy use. This study presents a multiscale assessment combining outdoor experiments, computational fluid dynamics (CFD), and annual building energy simulations. An outdoor small-scale BIPV platform was established to characterize cavity thermal behavior and validate the CFD model. The CFD model was used to investigate the effects of PV tilt angle, solar irradiance, and wind speed on cavity airflow, heat transfer, and photovoltaic performance. Annual EnergyPlus simulations were subsequently conducted to evaluate PV generation, building energy benefits, and cavity effects under different climatic conditions. The results showed that the maximum temperature of the PV modules on the building was reduced by 8.6 °C, with power generation increasing by nearly 4% due to the ventilation cavity. Solar irradiance dominated system output, whereas wind speed played a secondary role. Nationwide analysis based on the fixed 15° reference configuration showed pronounced spatial heterogeneity in photovoltaic potential. The ventilated cavity could either enhance or offset such benefits under different climatic conditions. Specifically, when local climate resulted in an annual cooling-load share exceeding 0.68, the cavity was more likely to produce a positive energy-saving effect. The energy saving potential varied significantly across different climatic conditions. 28.4% of areas in China have high climatic suitability for BIPV, including the southwestern, northwestern, and parts of the southern coastal regions. This study provided a quantitative basis for climate-specific design optimization and regional deployment of BIPV with ventilated cavities.