Role of pavement radiative and thermal properties in reducing excess heat in cities

Jyothis Anand, David J. Sailor

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

While pavements are currently a significant contributor to the urban heat island effect, modified pavements could play a role in cooling cities. Specifically, the radiative and thermal properties of pavements can be manipulated to alter the timing and magnitude of sensible heat storage and release into the urban airshed. The present study developed and applied a one-dimensional heat transfer model to Phoenix AZ as a case study to explore the potential for modified pavements in a hot desert climate. We explored solar reflective (0.35 albedo) and traditional (0.10 albedo) asphalt pavements. Pavement thermal conductivity and heat storage capacity values were varied across a reasonable range based on existing products. The results from this study show that daytime peak surface temperature of highly conductive (2.4 WK-1m−1) and thermally massive pavements (4.0 MJK-1m−3) is 17.5 °C cooler than less conductive (0.4 WK-1m−1) and thermally light (1.0 MJK-1m−3) pavements. However, at night, the more thermally massive and conductive pavements were as much as 10.8° C warmer than the less conductive and less massive counterpart. Therefore, when the focus is on reducing excess urban heat during the day, it is better to use pavement materials with higher conductivity and thermal storage. However, when the focus is on reducing the nocturnal heat island, it is wise to use lower conductivity and lower thermal storage pavements. Regardless of thermal properties, the use of reflective pavement surfaces will mitigate both the daytime and nocturnal urban heat island effect. We find up to a 10° C reduction in peak daytime surface temperature and a modest reduction of nocturnal temperatures (by up to 1.0° C) when pavement albedo is increased by 0.25. However, reflective pavements result in a higher influx of net radiation for pedestrians walking on these surfaces during the daytime. So, reflective pavement projects should be evaluated for potential adverse impacts on thermal comfort. Nevertheless, depending upon the time of day and the overall solar reflectivity of pedestrian clothing and skin, we argue that the benefits of reduced surface and air temperatures associated with highly reflective paving likely outweigh the adverse effects for pedestrians. However, for regions where daytime thermal comfort is of primary concern, pavements with higher thermal conductivity and thermal storage may perform better than reflective pavements.

Original languageEnglish
Pages (from-to)413-423
Number of pages11
JournalSolar Energy
Volume242
DOIs
StatePublished - Aug 2022
Externally publishedYes

Funding

The authors gratefully acknowledge the support of this work through a grant by ‘The Global KAITEKI Center,’ a research alliance between Arizona State University and The KAITEKI Institute of Mitsubishi Chemical Holdings Corporation.

FundersFunder number
KAITEKI Institute of Mitsubishi Chemical Holdings Corporation
Arizona State University

    Keywords

    • Cool pavements
    • Heat island mitigation
    • High albedo surfaces
    • Pedestrian heat gain
    • Urban heat islands

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