Optimal cover designs for outdoor units of air conditioners: A pathway to alleviate the hidden energy burden in Asian megacities

Aesthetic façade covers are widely installed across Asian megacities to conceal outdoor air conditioner (AC) units, yet their energy consequences remain poorly quantified amidst rising cooling demands. This study investigates the unsustainable energy burden imposed by these covers and proposes optimized designs to mitigate it. A comprehensive approach combining laboratory experiments, thermodynamic modeling, and building energy simulations was employed to systematically evaluate the impacts of two prevalent cover types across major Asian climate zones. The core of the methodology involved the development and parametric testing of optimized cover designs through adjustments to louver angles and orifice-plate porosities. Fully enclosed covers severely degraded AC performance, reducing cooling efficiency by up to 34% and increasing building cooling energy use by an average of 11.4 kWh/m2, with peaks exceeding 26 kWh/m2 in hotter regions. Cooling operation times were significantly extended, notably during extreme heat events. The results demonstrate that optimized covers can virtually eliminate this energy penalty. Louver covers with 60°/80° angles and orifice-plate covers with 30%/40% porosity limited the average increase in cooling energy consumption to a marginal 0.8 kWh/m2 reduction and 1.3 kWh/m2 increase, respectively, compared to uncovered units. The findings reveal that unregulated cover use poses a substantial threat to energy security in Asia. Therefore, it is imperative that these optimized structural parameters are integrated into building facade standards and policies, offering a viable pathway to reconcile urban aesthetics with sustainable cooling.