On-site investigation on operation status of floor-standing air conditioners and energy-saving strategy exploration in university classrooms of Nanning with hot-summer and warm-winter climate

To promote the construction of green campuses in hot-summer and warm-winter regions, this study takes 892 medium-sized classrooms across 16 teaching buildings in three universities in Nanning (a southern city in China) as research objects. Field measurements in a typical Guangxi University classroom were conducted to examine the operation of floor-standing air conditioners. Air-conditioning energy use constitutes a major portion of total campus building consumption, yet manual management lacks adaptability, causing mismatches between system operation and actual use, energy waste, and reduced thermal comfort. A combination of on-site investigation, thermal environment monitoring, questionnaire survey, and occupant behavior observation was employed to analyze equipment operation, indoor comfort, and usage patterns under different scenarios. Results show that floor-standing air conditioners represent 58.6% of all cooling equipment and dominate in medium-sized classrooms. However, their fixed air supply direction fails to respond to dynamic occupancy. In lecture classrooms, all units often run despite partial occupancy, while in study classrooms, operation is not adjusted to dispersed use—revealing systematic mismatches. Additionally, poor coordination with building factors such as solar radiation and window opening further increases cooling load. The study proposes differentiated energy-saving strategies for teaching and self-study scenarios through dynamic zoning control based on real-time occupancy. These findings provide empirical support for targeted retrofits of floor-standing air conditioners in universities. Future work will use numerical simulations to validate the proposed strategies and extend their applicability to classrooms of various sizes and orientations, contributing to a refined, generalizable energy-efficient control framework.