Adapting to Extreme Heat: Social, Infrastructure, and Atmospheric Impacts of Air Conditioning Adoption in Mega-Cities

Extreme heat events are becoming more frequent and intense in the majority of large cities. Built-up surfaces also limit cooling mechanisms, leading to warmer conditions in cities, a phenomenon called the Urban Heat Island (UHI). This presents major challenges to reduce adverse health effects of hot weather, particularly in vulnerable populations like the elderly, infants, and low-income communities. Here we explore the overall impacts of increasing A/C systems adoption in residences as an adaptive measure to reduce human health risks under heat waves, with New York City (NYC) as a case study. This study uses A/C adoption data from the 2017 New York City Housing and Vacancy Survey to study impacts to energy demand, household utility expenses, and UHI. Across NYC, this A/C adoption spans from 75.8% to 98.4% of homes.

The Weather Research and Forecasting (WRF) model, coupled with a multi-layer building environment parameterization and building energy model (BEP – BEM) is used to perform this analysis. The BEP – BEM schemes are improved and used as a tool to analyze current and full A/C adoption scenarios. A/C household fraction data are ingested into WRF to describe the spatial distribution of A/C use across NYC. A city-scale case study is performed over the summer months of June – July 2018, which includes an extreme heat event. Model results are validated with surface weather stations and with electricity demand for the whole city provided by the New York Independent System Operator (NYISO), showing good agreement in both cases. The impact of increasing A/C systems to 100% usage across NYC results in a peak energy demand increase of 27%, while the UHI is slightly increase on average by 0.42 ⁰C. Results highlight potential tradeoffs in extreme heat adaptation strategies for cities, which may be necessary.