Air-conditioning anthropogenic heat in high-density residential areas: Spatial patterns and impacts

Abstract

The overheated urban environment has drastically increased air-conditioning (AC) usage, which induces extensive heat emissions from outdoor units. This phenomenon is more adverse in high-density residential areas as the air-conditioning anthropogenic heat (ACAH) would further cause localized heat accumulation in canyons, negatively impacting AC energy consumption and residents’ comfort. While previous research has explored the impact of ACAH on urban canyons, there is a lack of studies that systematically investigate the pattern, impacts, and mitigations of ACAH at a refined scale in high-density residential areas. This study aims to investigate the temperature distribution under ACAH and quantify its impact on cooling energy consumption and pedestrian thermal discomfort. High-density residential areas were categorized by different heights of buildings and directions of outdoor unit placement. Numerical simulations were conducted to study ambient temperature distribution. Results showed that the worst heat accumulation was at the windward position of the AC outdoor unit, and the outdoor temperature on the middle floor was 2.3 °C higher than that on the upper floor, resulting in a higher energy consumption of 6.3 W/m2. The worst case with taller windward buildings caused 55 % of the pedestrian areas to be more uncomfortable. Mitigation strategies were also proposed from multiple perspectives, including heat source optimization (e.g., cross-layout of AC outdoor units) and offering subsidies for AC electricity consumption gaps. The study provides a systematic research perspective on spatial heat accumulation patterns in high-density residential areas, which is instructive for mitigating urban warming and promoting sustainable urban development.