Moderating AC Usage Can Reduce Thermal Disparity between Indoor and Outdoor Environments

Area of Science:

• Urban Climatology
• Building Energy Systems
• Climate Change Adaptation

Background:

• Climate change intensifies urban heat events, increasing reliance on air conditioning (AC).
• AC use creates a conflict between indoor thermal comfort and outdoor heat stress, with limited scientific guidance on balancing these.
• Megacities face unique challenges due to high energy demand and infrastructure.

Purpose of the Study:

• To investigate the trade-offs between indoor thermal comfort and outdoor heat impacts from AC usage.
• To develop and apply a coupled modeling approach for simulating AC impacts in a megacity.
• To identify strategies for optimizing AC energy consumption and mitigating negative environmental effects.

Main Methods:

• Coupled modeling integrating Weather Research and Forecasting (WRF) with a Building Energy Model (BEM).
• Simulation of multiple AC usage scenarios in Chongqing, China.
• Analysis of indoor temperature, outdoor thermal comfort, and electricity demand.

Main Results:

• AC significantly reduces indoor temperatures (up to 18 °C) but causes nighttime outdoor warming (2-2.5 °C) and reduces thermal comfort.
• Increasing indoor temperature by 2 °C can alleviate outdoor temperatures by up to 1 °C, especially in dense areas.
• Reducing spatial cooled fraction (up to 50%) and implementing temporal AC schedules are effective for lowering energy consumption in high-density neighborhoods.

Conclusions:

• Balancing indoor comfort and outdoor heat requires careful AC management strategies.
• Optimizing AC use, particularly in dense urban areas, is crucial for energy efficiency and mitigating urban heat.
• Reassessing energy resilience and promoting thermal equity are vital for sustainable urban climate strategies.