External Temperature Distribution and Characteristics of Building-Integrated Photovoltaics (BIPV) Under Summer High-Temperature Conditions

This study investigates the external environmental temperature distribution of a small single-story BIPV building on a university campus in Jinan City, Shandong Province, China, under the most adverse summer high-temperature conditions. The temporal and spatial distribution characteristics and variation patterns of building external temperature are analyzed. The results indicated the following: (1) During summer high-temperature days, the peak temperature of the BIPV photovoltaic surface reached 52.4 °C, which is 17.4 °C higher than the ambient temperature. (2) External measurement points exhibited significant daytime heating (+2.86 °C) and nighttime cooling (average relative temperature increment of −1.52 °C). (3) Complex nonlinear temperature gradient variations existed within the 10–100 cm range from the surface, with localized heat accumulation occurring around 60 cm, where 77% of high-temperature days show temperature gradient anomalies. (4) Based on dimensionless analysis, a modified Richardson criterion for BIPV buildings is established: Ri < 0.3 represents building-geometry-dominated mechanisms, and Ri > 0.7 represents thermal-plume-dominated mechanisms. The critical values occur earlier than in classical theory. (5) Solar radiation and wind speed are key factors affecting temperature distribution, with more pronounced local heat accumulation under low-wind-speed conditions. This study provides scientific evidence for BIPV building performance optimization and environmental control.