Under extreme high-temperature conditions, heat accumulation in rooftop photovoltaic (PV) arrays can substantially reduce PV conversion efficiency and output power. To improve the thermal and power-generation performance of rooftop PV systems, this study developed a computational fluid dynamics (CFD) model for a rooftop PV array and validated it using field measurements from Chongqing, China. The relative root mean square errors (rRMSEs) between simulated and measured backsheet temperatures at the three measurement points were 6.31%, 7.52%, and 8.45%, respectively, indicating acceptable model accuracy. The effects of mounting height, tilt angle, and front-to-rear row spacing on PV backsheet temperature, conversion efficiency, and output power were then investigated. A central composite design (CCD) within response surface methodology (RSM) was used to establish regression models linking the design variables to the objective functions. Finally, an NSGA-III-based multi-objective optimization framework combined with TOPSIS was used to identify the optimal configuration. For the rooftop PV array studied under extreme summer conditions in Chongqing, the TOPSIS-selected compromise solution corresponded to a mounting height of 0.90 m, a tilt angle of 15.63°, and a front-to-rear row spacing of 2.96 m. Compared with the original configuration, the optimized passive installation geometry reduced the peak PV backsheet temperature by 2.3 °C without active cooling, water consumption, or additional energy input. Under the same meteorological and irradiance conditions, this temperature reduction increased conversion efficiency by 0.5% and output power by 0.4%. Detailed inter-row short-wave shading and electrical mismatch were not explicitly modeled. Therefore, the row-spacing effect mainly reflects changes in ventilation and module temperature under the same irradiance input. The proposed framework provides a practical reference for installing and optimizing rooftop PV arrays in hot-climate regions.

Energy saving strategy of highway tunnel lighting mainly concentrated on shading facilities at tunnel entrances and exits, lighting intelligent control systems and lighting design methods. The contrast revealing coefficient q_c is widely recognized as a key index used to assess the quality of tunnel lighting. The optimal values of the contrast revealing coefficient are associated with the optimal visual effecicy in tunnel lighting. This study aimed to give a new energy saving strategy based on optimal luminaire installation methods. Light Emitting Diode lamps (LED) were selected in tunnel lighting simulation experiment. The optimal luminaire installation method was determined by considering both the lighting quality evaluation system and the optimal value of the contrast revealing coefficient. Then, the lighting conditions achieved through the optimal luminaire installation method can be assessed based on the detection distance of small targets. Results showed that lighting environment under optimal luminaire installation method can fulfill the criteria for safe driving and visual comfort. Compared with the original luminaire installation method, the optimal luminaire installation method can save 24.32% of electrical energy.

Visual fatigue is a serious issue among Chinese secondary school students owing to prolonged daily exposure (8–10 h) to visual display terminals (VDTs) in widely equipped multimedia classrooms. To mitigate such effects, this exploratory study identifies promising lighting parameters by evaluating the influence of blackboard reflection coefficients, the ratio of desktop illumination to blackboard illumination, and correlated color temperature (CCT) in a simulated multimedia classroom environment. Thirteen participants performed visual tasks (Landolt ring visual acuity tests and Anfimov’s Chart Task) under various conditions. Visual fatigue scale (VFS-10), index of mental capacity (IMC), and eye movement parameters (EMP) were used to assess visual fatigue and efficiency. Results suggest that higher blackboard reflection coefficients improved efficiency and reduced fatigue. Increased blackboard illumination alleviated fatigue at constant CCT, whereas changes in desktop illumination showed no significant effect. The highest efficiency among the tested CCT values was observed at 4700 K, while visual fatigue was minimized at 4000 K. The findings provide preliminary practical applications for minimizing visual fatigue and improving performance efficiency in secondary school multimedia classroom environments equipped with VDTs.

Respiratory infectious diseases pose substantial transmission risks in enclosed public-transport environments. Under a defined fully seated reference scenario, this study examines whether the same HVAC supply parameter governs two respiratory-particle control objectives in a subway carriage: whole-carriage particle removal and local seated breathing-zone exposure. Computational fluid dynamics (CFD) simulations, single-factor analyses, an L16 orthogonal design, analysis of variance (ANOVA), and grey relational analysis (GRA) were used to evaluate supply velocity, temperature, and angle. The results reveal an objective-dependent control hierarchy. Supply velocity is the leading factor for whole-carriage removal (contribution rate, 40.14%; p = 0.047), whereas supply angle contributes most to the seated breathing-zone particle proportion (59.30%), although the corresponding ANOVA result does not reach statistical significance at the 0.05 level (p = 0.056). The two single-objective optima share the same velocity and angle but differ in temperature, indicating a partial rather than complete mismatch. GRA identifies 2.0 m/s, 24 °C, and 0° as the best compromise among the investigated cases. This combination is specific to the modeled carriage, passenger arrangement, source location, and operating conditions. The more generalizable finding is that global clearance and local breathing-zone exposure are governed by different control variables.