Anthropogenic heating of the urban environment due to air conditioning

Abstract

This article investigates the effect of air conditioning (AC) systems on air temperature and examines their electricity consumption for a semiarid urban environment. We simulate a 10 day extreme heat period over the Phoenix metropolitan area (U.S.) with the Weather Research and Forecasting model coupled to a multilayer building energy scheme. The performance of the modeling system is evaluated against 10 Arizona Meteorological Network weather stations and one weather station maintained by the National Weather Service for air temperature, wind speed, and wind direction. We show that explicit representation of waste heat from air conditioning systems improved the 2 m air temperature correspondence to observations. Waste heat release from AC systems was maximum during the day, but the mean effect was negligible near the surface. However, during the night, heat emitted from AC systems increased the mean 2 m air temperature by more than 1°C for some urban locations. The AC systems modified the thermal stratification of the urban boundary layer, promoting vertical mixing during nighttime hours. The anthropogenic processes examined here (i.e., explicit representation of urban energy consumption processes due to AC systems) require incorporation in future meteorological and climate investigations to improve weather and climate predictability. Our results demonstrate that releasing waste heat into the ambient environment exacerbates the nocturnal urban heat island and increases cooling demands.

The Impact of Subsidies on the Prevalence of Climate-Sensitive Residential Buildings in Malaysia

“…The model results confirm the growing trends in AC ownership and usage observed elsewhere [1,2]. Residential CSB design presents an alternative risk mitigation approach, decreasing exposure to heat by providing a cooler indoor environment and reducing the AC contribution to the UHI, estimated between 0.2-2.6 • C [10][11][12][13][14][15][16]. Model results show that the potential for CSB adoption to reduce AC use and associated UHI effects is limited, especially for large increases in ambient temperatures.…”

“…It also creates local challenges in these countries. Indeed, AC usage (1) is changing electricity usage patterns [4][5][6], thereby increasing the risk of major power outages, especially during heatwaves [5,[7][8][9]; (2) contributes to night-time urban heat island (UHI) intensity, [10][11][12][13][14][15][16], impacting sleep quality and increasing health risks, especially for AC non-users [17][18][19]; and (3) increases the frequency of respiratory illness [20][21][22][23]. These local and global impacts point toward a need for alternative cooling solutions.…”

Citywide Impacts of Cool Roof and Rooftop Solar Photovoltaic Deployment on Near-Surface Air Temperature and Cooling Energy Demand

“…For the non-urban part, land-use categories were implemented using the MODIS satellite land-cover classification. Building morphological characteristics and thermal properties for roofs, roads, and vertical walls were obtained from Burian et al (2002) and Clarke et al (1991), and are detailed in Salamanca et al (2013Salamanca et al ( , 2014Salamanca et al ( , 2015. During the 10-day extreme heat period it was assumed that every building made use of air-conditioning systems and the resulting anthropogenic heat was rejected as sensible heat into the urban environment.…”

Internet-Based Heat Evaluation and Assessment Tool (I-HEAT): Feasibility Analysis of a Visualization and Decision-support Tool for Extreme Heat Preparedness in Detroit, Michigan

“…U.S. metropolitan centers are projected to grow significantly by the mid to late century; larger and older populations will be living in urban areas (Frumkin 2002) with higher ambient temperatures, potentially leading to a larger-magnitude impact of extreme heat on human health. Some adaptive measures, such as increasing air conditioning prevalence and usage, can limit individual and short-term exposure to extreme heat-but they can also increase ambient temperatures (Sailor and Pavlova 2003) and contribute to global climate change via the release of greenhouse gases and latent heat expenditure (Salamanca et al 2014). It is critical to consider the net effect of adaptive measures when identifying ways to reduce future risk of extreme heat.…”